Photo illustration by Kelly Martin

1,400%: Expected increase in 95-plus degree days in Montgomery County between the historical baseline and 2100(1)
5.1 degrees: Expected increase in average annual temperatures in the Northeast by 2050 as compared with 1975-2005(2)
1 inch: Monthly precipitation increase projected for December through April by 2100
in the Northeast(3)

(1) Projection based on RCP 8.5 (high emissions scenario); Source: Montgomery County Climate Action Plan, published 2021. (2 and 3) Projections based on RCP 8.5 (high emissions scenario); Source: 2018 National Climate Assessment.


Hurricane Ida had already ravaged Louisiana and much of the South as its remnants barreled northeast last summer. In the overnight hours leading into Sept. 1, the storm deposited 3.3 inches of rain in barely an hour in the Rockville/Twinbrook area.

First responders arriving with boats and a dive team at the Rock Creek Woods apartments on Twinbrook Parkway in Rockville found a “significant number of residents…outside screaming that people were trapped in these buildings,” according to Montgomery County Fire and Rescue Service (MCFRS) reports. Rescue personnel also encountered language barriers among the immigrants who accounted for a significant number of residents in the complex.

Inside, first responders discovered two ground-level apartments “completely under water.” They broke a sliding glass door to find barely 6 inches of air between the water and the ceiling in one unit, while managing to rescue a woman holding a baby. “Interior stairs were completely full of water to the point you could not see the hallway doors or door jambs,” one report says.

Melkin “Melky” Daniel Cedillo, a Richard Montgomery High School alumnus and a busser at Iron Age restaurant in Rockville, was one of the residents. The 19-year-old Honduran immigrant escaped a flooded apartment but went back for his mother.

Rescuers saved six people from those two ground-level units, and a total of 16 from two buildings in the Rock Creek Woods complex. They could not save Cedillo.

“I never imagined that my son was drowning there,” his mother, Daisy, told Telemundo 44 in Spanish last September as she sobbed into a tissue. “My God, this pain is too much for me.”

Four people were taken to hospitals, and 150 residents were displaced.

The tragic episode serves as testament to the face of climate change in Montgomery County—and what’s increasingly forecasted for its residents in the coming decades, with the heaviest impacts likely falling on those with the fewest resources.

Montgomery County’s Climate Action Plan, published three months before the flooding at Rock Creek Woods, is hauntingly prophetic, reading: “Urban flooding disproportionately affects low-income residents and communities of color because the majority live in neighborhoods with little or no green spaces to absorb water, and in areas that have historically received less flood protection investment. In addition, these communities tend to live in basement or ground-floor apartments, which are hit hardest by urban flooding.”

Ida, which slammed New Orleans with maximum sustained winds of 150 mph, was one of 21 named storms last year, considered the third-most active year for hurricanes on record. Climate change is intensifying hurricanes, boosting short-term rainfall amounts and increasing storm surge, according to experts and data.

Montgomery County is largely protected from rising sea levels. Yet forecasts indicate that the impacts of climate change, particularly on temperature and precipitation, will be seen in multiple ways across the county, now and in coming years.

The Climate Action Plan, which describes predicted impacts of climate change and lays out a roadmap to reduce greenhouse gas emissions, says extreme heat may pose the most severe local threat to health and the environment. If ambitious efforts in Montgomery County and elsewhere to curb greenhouse gas emissions fall short, the county is slated to experience a 1,400% increase in 95-plus degree days between now and 2100, according to the plan.

And when it comes to the threat of intense precipitation, “the future is already here,” says William Musico, floodplain administrator at the county’s Department of Permitting Services.

Sligo Creek flooded its banks last August, and the water rushed into Sligo Creek Parkway at New Hampshire Avenue, pushing cars off the road and prompting at least one water rescue from a car. Photo by Getty Images

On Sept. 10, 2020, almost a year before the Twinbrook inundation, a high-quality rain gauge near Kensington’s town hall—part of a nationwide volunteer monitoring network—measured 4.69 inches of precipitation in five hours, most of it falling in two hours. MCFRS responded to 50 reports of vehicles trapped in high water in Kensington and surrounding areas.

At his home in the northern portion of the adjacent municipality of Chevy Chase View, energy consultant David Goldwyn—later named to chair a stormwater management committee for the town of Chevy Chase View—witnessed water migrating from higher ground rise to a height of nearly 3 feet in his backyard as he mopped and bailed in the lower level of his residence.

In nearby Kensington Estates that day, rising waters flooded vehicles and moved many from their parking spots.

As Goldwyn notes, “This Sept. 10 storm was really not a one-off occurrence. [It] was one of three such events [over] five years.” In response to damage sustained by his home during a May 2016 storm, he contracted for construction work to protect against future flooding—only to see those efforts overwhelmed by the intensity and volume of precipitation during the September 2020 event.

A survey commissioned by the town council following that storm found that in Chevy Chase View—with its population of about 1,000—at least 20% of property owners suffered flooding of homes or other adverse effects.

“We were lucky no one was harmed in this storm, but the health and safety risk is real,” Goldwyn told the Chevy Chase View council in late July 2021, weeks before Cedillo lost his life in the Twinbrook flooding.

The episodes are becoming more common across the region.

“The recent dominant trend in precipitation throughout the Northeast has been towards increases in rainfall intensity…exceeding those in other regions in the contiguous United States,” according to the latest National Climate Assessment, published by several federal agencies in 2018.

A prior version of the National Climate Assessment, published in 2014, shows a 71% increase in heavy precipitation events in the Northeast from 1958-2012—almost twice the next highest increase among regions of the United States. In Montgomery County, urban flooding has spiked from two to four episodes annually before 2010 to an annual range of 11 to 39 occurrences, according to an analysis last year by the County Council’s Office of Legislative Oversight.

The difficulty in forecasting where and when such extreme events will occur adds to their threat. “One of the challenges of climate change is that it throws our normal weather and climate patterns out of whack,” says Adriana Hochberg, Montgomery County’s climate change officer. “Things become much more unpredictable, and there are these swings—various levels of extremes—so that you can’t really plan ahead.”

Alluding to the Twinbrook storm, Hochberg underscores that no section of the county is immune from the prospect of such catastrophic events in the near future. “If that weather pattern had moved just 3 miles north, it could have happened in Olney, versus Twinbrook,” she says.

While it is not a new occurrence to have hurricanes—or their remnants—hit Maryland, scientists say climate change has increased their impact.

“With hurricanes, we’re seeing slower-moving storms around the U.S.,” causing them to linger overhead for a longer period, says Kelly Halimeda Kilbourne, an associate research professor at the University of Maryland Center for Environmental Science (UMCES). “We also see…stronger winds, and with the intensity of the winds and the actual motion of the storm you end up with really intense bands [of precipitation] that cause those intense rain events within the storm.”

At one point during the Twinbrook storm, 2.4 inches of rain fell within just a half hour, according to the National Weather Service. “The most intense portion of the storm was characterized as a 300-year storm for that half-hour time period,” officials at the Montgomery County Department of Transportation told Hochberg.

Terms such as “100-year storm” and “300-year storm” are popular parlance for what is known in professional circles as the “return period.” For example, in the case of a 100-year storm, the chances of an event of that magnitude occurring in a given year is considered to be 1%.

The problem is that such assessments are lagging behind present-day reality. They are based on a National Oceanic and Atmospheric Administration (NOAA) document utilizing rainfall data that has not been updated in more than 20 years. Rainfall data for the region including Maryland is now being redone, with completion of the project about three years away, according to Musico and Kilbourne.

In Ellicott City in Howard County—barely 20 miles north of the Montgomery County border—6.6 inches of rain fell in a three-hour period on July 30, 2016, according to NOAA. The rainfall earned that event the rating of a 1,000-year storm, meaning that there was a one-tenth of 1% chance of it happening in a given year. But an identical event occurred in exactly the same location less than two years later, on May 27, 2018, when 6.56 inches of rain fell, also within a three-hour period, according to NOAA.

“The basic nomenclature of the 1,000-year storm is really based on a mid-20th century understanding of climate being stable,” Kilbourne says. “[That] doesn’t exist anymore.”

The changes in the environment that are producing more— and more violent—precipitation here will also shift average temperatures upward and produce more days of scorching heat, according to experts and data.

“The most significant changes from today’s climate conditions…appear to be related to extreme heat,” states the Climate Action Plan. The county’s utilities, homes and people will have the greatest exposure and sensitivity to these shifts, according to the plan. For instance, power substations are very vulnerable to heat, which can stress electric infrastructure and cause outages.

But it’s the impact on homes and people that underscores the inequity in climate change, according to the plan. Factors exacerbating the impact include “heat islands” which contain dense populations, lots of impermeable surfaces and little tree shade, “high-exposure occupations” such as construction and landscaping, and reliance on “high-exposure modes of transportation” like transit and walking.

“Montgomery County is going to see higher temperatures in both winter and summer, and it’s going to come with a whole bunch of adaptations that are necessary to maintain a high quality of life,” says Andrew Elmore, professor of landscape ecology at UMCES’ Appalachian Laboratory in Frostburg, Maryland. He also has this warning: “You’re going to see more people dying of high heat in some parts of urban areas.”

Among the adaptations is greater access to and the use of air conditioning—which brings with it another set of issues related to social equity and the environment.

Much of today’s air conditioning is powered by electricity generated by fossil fuel-burning plants that contribute to greenhouse gas emissions. Even as Maryland strives to meet a 2030 legislative deadline for half of its electricity to be generated by renewable sources, refrigerants used by air conditioners also contribute to global warming.

Heat pumps are an emerging alternative that can transfer heat to the outdoors during hot weather, but the average cost of retrofitting homes with a variety of systems to reduce carbon emissions (pegged at about $70,000 per household by Rewiring America, a nonprofit group that advocates such efforts) highlights what the Climate Action Plan terms the “climate gap.” It notes that residents of color are more likely to be “disproportionately affected by climate change, yet have the least resources and less ability to cope with and respond and adapt to its impacts.”

“Extreme heat is even more severe for populations living in substandard housing that may not have air conditioning. …Moreover, unless cooling retrofits are made financially accessible, low-income residents will be faced with the wrenching choice between running the air conditioners or dealing with the intense heat to save money,” the plan adds.

Though the county aims to eliminate greenhouse gas emissions by 2035, young activists expect to see the impacts continue to worsen in their lifetime.

Hasham Khan, a 17-year-old senior at Watkins Mill High School in Gaithersburg, immigrated to Montgomery County from Pakistan with his parents when he was 5. He has participated in several demonstrations pressing for action on climate change. One of his top priorities is “an emphasis on closing the poverty gap, because climate change will only widen it more. Resource wars will become the common thing.”

He adds, “In Montgomery County, we’re…more developed than India and Pakistan. But we still have to know that resources drying up means that poorer people will be left to scramble for what’s left, while the richer off can make do with what they have.”

Khan worries about whether the political will exists, at home and abroad, to avoid what he fears will become a “huge humanitarian disaster” during his adult years.

Matt Fitzpatrick, associate director for research at UMCES’ Appalachian Laboratory, has designed an online tool that allows users to determine which areas of the country will most resemble the temperature of their current home location in 2080. The results for the Washington, D.C., area: Summers nearly six decades from now could feature temperatures similar to current-day Greenwood, Mississippi—less than 300 miles north of New Orleans—where the typical summer is now 6.4 degrees warmer than D.C.

That calculation assumes that efforts to significantly reduce greenhouse gas emissions by midcentury will fall short. According to data in the Climate Action Plan, the county’s historical climate baseline (a period from 1950 to 2005) has indicated about four days a year in which the local temperature tops 95 degrees.

By 2100, the number of such days is calculated to jump to at least 28 annually, even under a best-case scenario for controlling greenhouse gas emissions, according to the plan. That projection assumes a leveling off of greenhouse gas emissions after 2050 under what the Intergovernmental Panel on Climate Change has dubbed RCP (Representative Concentration Pathway) 4.5. The worst case, RCP 8.5—the so-called “business as usual scenario”—would yield 60 days annually of 95 degrees or higher by 2100.

“It’s important to point out that the increase in 95-degree days doesn’t even factor in the impact of humidity,” Hochberg says. “Another aspect [is that] in the nighttime in summer—and we’ve already started to experience this—temperatures are not going to be cooling down. Everybody needs that for public health, and we’re not going to be getting that.”

Even if the county achieves its goals of reducing greenhouse gas emissions 80% by 2027 and 100% by 2035 (it was only 19% of the way there as of 2018, the last year for which figures are available), the specter of two months of 95-plus degree days locally will continue to loom if similar reductions are not achieved worldwide.

To achieve RCP 4.5 “globally, you’re saying everybody is coming into line, so that by the middle of the century, emissions will have peaked and we’ll be going on a downward trajectory,” Hochberg says. But, she adds: “We’re not on that path right now. We’re very much on the 8.5 RCP path.”

As it grapples with how to remain on a trajectory to potentially head off the heat, the county also faces a major financial and political challenge that exists right now: how to alleviate the impact of the increasing instances of severe flooding brought on by intense storms, for which extreme heat will only provide additional fuel.

“The stormwater management system has limited adaptive capacity, particularly as storms become more intense in the future, and the existing system is underdesigned,” the Climate Action Plan concedes. During the generation since much of the system was built, the county’s growth has resulted in the construction of larger homes and an increase in impervious surfaces, from which water runs off rather than being absorbed.

It’s a challenge that the county government, along with other state and regional agencies with jurisdiction in the area, is only beginning to address.

“According to stakeholders, the county is barely meeting investment needs for maintaining existing infrastructure, let alone future risks,” the Office of Legislative Oversight declares in an April 2021 report. “There is a lack of climate data available, and available data is siloed in county departments (often offline). Stakeholders also report a lack of expertise among county staff to understand the extent of climate risks and adaptation strategies necessary to protect critical infrastructure.”

Hochberg, who is also serving as acting director of the Department of Environmental Protection, says county government is in the “initial stages” of centralizing climate data and determining what additional data ought to be collected.

At the same time, in the wake of last September’s Twinbrook flood, the county established an interdepartmental task force to examine “where is flooding happening, where is it likely to happen in the future, and how do we keep people and property safe from it,” she says. “We know that these flooding events are going to continue, and that they’re going to get exacerbated as we move forward. And we need to move from a reactive stance to a proactive stance.”

As Goldwyn succinctly put it while speaking to the Chevy Chase View Council last summer: “Essentially, the gray infrastructure is undersized and the green infrastructure is underutilized.”

“Gray infrastructure” is a reference to the network of stormwater pipes, drains and inlets that development in the county has outgrown; “green infrastructure” refers to so-called “environmental site design” that allows greater absorption of rainfall before water migrates and contributes to flooding in other locations. Such measures have run into political resistance in some neighborhoods over concerns about possible restrictions on uses of private properties and adjacent streets.

“It is going to be a very significantly expensive project to upgrade our stormwater management system, with a lot of complexities in permitting that are going to take years for us to sort through,” says County Council President Gabe Albornoz, whose Kensington residence is located near the site of the September 2020 flooding.

He adds ruefully, “In the meantime, local neighborhoods are experiencing really life-altering kinds of incidents.”


Montgomery County’s risk and readiness

Montgomery County’s Climate Action Plan, issued in 2021, examined different sectors of the county, such as critical and community resources (schools, hospitals, police stations and shelters), and studied how much these areas could be exposed to climate change; how sensitive they likely would be to impacts; and how well they could potentially adapt. The county determined that precipitation, temperature (mostly heat), drought and wind would reflect the biggest shifts between current conditions and 2100.

Total homes in Montgomery County: 404,057

County homes in, or within 500 feet of, FEMA floodplain*: 38,491

Percent of total homes: 9.5%

*Designed by FEMA as any land area susceptible to being inundated by floodwaters from any source.

Source: Montgomery County Climate Action Plan, published 2021.


A cover crop, which promotes soil health and conservation, in the Agricultural Reserve. Photo by Montgomery County Office of Agriculture

In the Ag Reserve

Montgomery County has experienced intense development in recent decades, but much of its northern section has been protected following the creation in 1980 of the Agricultural Reserve, which encompasses almost one-third of the county’s total acreage.

Climate change has created challenges there, with changing weather patterns affecting the growing season.

In 2020 and 2021, “March and April have gotten together and agreed to switch: March decided to be warm and April decided to be cold,” observes Jeremy Criss, director of the county’s Office of Agricultural Services. “That is the worst thing for blossoms that come out on fruit trees that are real tender. If they are subjected to frost, the blossom’s dead.”

About 15% of nearly 560 farms in the county engage in fruit production, according to statistics kept by Criss’ office.

“[We] are concerned about the future of fruit production in the county, given some of these weather cycles,” he says.

Gene Kingsbury, who has been growing peaches for a half-century at his orchard near Dickerson, experienced extensive spring frost damage in 2020 and 2021. “In the 1970s and 1980s, we typically looked for peaches to bloom during the second week of April. For the past 10 years, we have been lucky to make it to the first of April. …Every day makes a difference when the threshold for frost damage is 29 degrees.”

Robert Butz says a May 2020 freeze was “hugely damaging” to the grape harvest at his Darnestown farm. To deal with it, he brought in a helicopter to hover over his orchards in the predawn hours one morning to combat a so-called “thermal inversion,” when cold air from the upper atmosphere descended to the ground, displacing warm air. Flying just 500 feet above, the prop wash from the helicopter pushed the warm air back down, enabling Butz to save the crop of one of his three vineyards. The helicopter rental cost him nearly $7,000.

“Frost damage…doesn’t usually occur until the sun rises,” Butz says. “It’s the combination of the photosynthetic energy on the frozen tissue that causes it to burst, rupture and die.”

There has been a silver lining for some farmers here. “The warmer and wetter conditions…should generally be viewed as positive by row-crop farmers. And on my farm, at least, yields over the last few years have been above our long-term trend,” says Butz, an owner of Windridge Vineyards, a diversified family farm that also grows row crops such as corn and soybeans.

At the same time, drought looms as a leading threat to the Ag Reserve as well as the county at large, according to the county’s Climate Action Plan released last year.

“Are we ever going to have Western-style massive droughts? Probably not,” says Kelly Halimeda Kilbourne, an associate research professor at the University of Maryland Center for Environmental Science. “The issue here is…agricultural drought, where you have two or three weeks with reduced or little rain, and that can cause serious problems for agriculture.”

Butz first planted grapes on his farm 11 years ago “to try to prepare for and adapt to climate change,” amid predictions of “warmer but drier”conditions.

He adds: “Responding and adapting to climate change is something we take seriously… and give a lot of thought to. …Our farm’s approach has been to diversify our crops to hedge against an unknown climate future.” 


The heat is on

Montgomery County officials have forecasted the increase in 95-plus degree days based on two models: RCP 4.5 (big cuts to greenhouse gas emissions) and RCP 8.5 (high emissions).

Louis Peck has written about politics as well as environmental issues over a five-decade career as a journalist. He can be reached at lou.peck@bethesdamagazine.com.