DC’s hard pivot towards autumn

 

A late summer day in Potomac, Maryland

The first three weeks of September have featured plenty of summer-like weather in the nation’s capital. However, it’s not uncommon for the second half of September to pivot to cooler, more fall-like temperatures. Such will be the case this week with the arrival of rainy and cooler than average weather.

These rainy and cool than average conditions will largely be the function of a nearby front and an anticipated area of low pressure that will develop along it near the Mid-Atlantic coast. That will help produce waves of rain and cooler than average conditions for the DMV (DC, Maryland and Virginia). That’s good news as the nation’s capital still has a year-to-date rainfall deficit of more than 6.5”.

As cool as the final week of September will be, the first 20 days of September only saw two cooler than average days. In fact, September began with four consecutive days of 90-degree heat in Washington, D.C. for the first time since 2015. Although no record high temperatures were set, three record high-low temperatures were tied earlier this month. That means three days remained unusually warm overnight. 

As of September 20, this month has been 3.7° warmer than average. If the final week of September were to feature similar weather conditions, then this month could have ranked among DC’s Top 10 warmest. However, with this week’s temperatures remaining appreciably below average and feeling more like mid to late October, September 2026 will finish with much closer to average temperatures.

This week’s rainfall will be beneficial as the DMV has battled drought conditions for much of the year. If this month finishes as a wetter than average month, it would become DC’s first wetter than average September since 2021. September is actually DC’s fourth rainiest month of the year with a monthly average of 3.93”, according to NOAA. That also takes into account beneficial rainfall from the remnants of tropical systems.

Montgomery County is spearheading sustainability projects

 

Great Falls, Maryland

Montgomery County, Maryland, secured an $8.3 million investment in state funding this summer to support clean energy and energy-efficient projects. This is significant since the implementation of energy-efficient technology can help reduce greenhouse gas emissions and improve air quality. Greenhouse gases, such as methane and carbon dioxide, are byproducts of the burning of fossil fuels in energy production and automobile emissions.

Montgomery County is Maryland’s most populous county with over a million residents and includes towns such as Bethesda, Silver Spring, and Rockville. Approximately $7 million of this grant money has been allocated to renewable energy projects with another $1.3 million to be used on energy-efficiency improvements. This initiative is estimated to save taxpayers $439,000 annually in energy costs.

The funding was awarded through Maryland’s Energy Administration's FY26 Local Government Energy Modernization (L-GEM) Program. Its goal is to reduce greenhouse gas emissions and promote clean energy and economic development.

Some of the 20 projects this state grant will go toward include:

• Installation of solar-powered backup systems at recreation centers and parks.
• Advancing Montgomery County's resilience hub and microgrid initiative.
• Improving safety, lighting, and energy efficiency in public parking facilities.

Montgomery County Council President Natali Fani-González said, “The more than $8 million funding from the Maryland Energy Administration will help Montgomery County advance clean-energy projects that reflect our sustainability-aligned values.” This underscores the common public sentiment among Montgomery County residents about the importance of sustainability and energy efficiency.

The reduction of greenhouse gas emissions is also essential to help mitigate the impacts of human-induced climate change. Although climate change is a naturally occurring phenomenon, it has advanced more rapidly in recent decades, largely due to human activities since the Industrial Revolution. According to the United Nations Intergovernmental Panel on Climate Change, “Since systematic scientific assessments began in the 1970s, the influence of human activity on the warming of the climate system has evolved from theory to established fact” (2021).

Through careful planning, this state funding will be put to good use in support of clean energy and energy-efficient projects across Montgomery County.

A closer look at September’s severe weather

 

The Enhanced Fujita Scale (Source: NOAA)

Severe weather is defined as a thunderstorm that contains any of the following: wind gusts of at least 58 mph, hail 1”/+ in diameter, or a tornado. Although it’s less common in September than during the spring and early summer, severe weather does occur. The remnants of tropical storms and hurricanes can also be a significant contributor to severe weather this time of year. 

2024:  Hurricane Helene was a devastating Category 4 hurricane that had far-reaching impacts in areas well inland both before and after its September 27 landfall in the Florida panhandle. A large and powerful storm, Helene and its remnants spawned dozens of tornadoes between September 25 – 27. The most active severe weather day was September 26 when 17 tornadoes touched down in South Carolina.

2023: The first half of September was quite hot in the DMV (DC, Maryland and Virginia) with plenty of record heat. Not surprisingly, there was no shortage of severe weather between September 7 – 9. There were dozens of large hail and damaging wind reports in DC, Maryland and Virginia. According to NOAA, a wind gust of 75 mph occurred in Williamsport, Maryland on September 7 and hail 1.25” in diameter was observed near Dulles Airport in northern Virginia on September 8.

2020: A small but significant severe weather outbreak occurred in the DMV on September 3. Several reports of severe wind gusts were reported with a variety of damage that ranged from downed trees and power lines to roof damage. An EF-1 tornado also developed in Anne Arundel County, Maryland that tracked over six miles, according to NOAA.  

2018: Hurricane Florence made landfall on September 14 and its remnants lingered for several days, bringing devastating flooding and severe weather to the Mid-Atlantic Region. The DMV experienced significant impacts on September 17-18, with 13 confirmed tornadoes in Virginia alone. The strongest was an EF-2 tornado on the Enhanced Fujita Scale with wind speeds of 115-125 mph. A September 18 record rainfall total of 2.22” occurred at BWI Airport.

2001: September 24 will be the 25^th anniversary of the deadly F3 College Park tornado that claimed the lives of two sisters who were caught in their car on the campus of the University of Maryland. At peak intensity, the tornado had winds of nearly 200 mph. Although it was ranked an F3 at the time, the College Park tornado would be a borderline EF4/EF5 tornado today. The College Park tornado was one of several, including an F4 in Culpeper County, Virginia that touched down across the DMV.