Lexington is asking residents to clear leaves and debris from storm drains before a nor'easter arrives as early as Friday, Sept. 25, a request that carries extra weight with days of heavy rain in the forecast.

The town posted a Stormwater Awareness Week notice on Tuesday, Sept. 22, reminding residents that runoff from roads, rooftops and driveways can carry pollutants into local waterways. Lexington sits within three watersheds: the Charles River, Mystic River and Shawsheen River. Whatever flows into the town's catch basins eventually reaches those rivers.

The timing matters. A nor'easter is expected to bring heavy rain to Massachusetts starting as early as Friday and lasting through Monday, according to Boston 25 News. Chief Meteorologist Shiri Spear said the storm's "impact window is going to be Friday through Monday." Inland areas could see 1 to 2 inches of rain.

Blocked drains mean flooded streets.

The town's notice warns that leaves collecting around catch basins can block water flow and cause localized flooding during heavy rain. Decomposing leaves also release phosphorus, which can fuel algae growth and harm aquatic ecosystems.

The town listed several steps residents can take: keep leaves and yard debris away from catch basins, pick up pet waste, dispose of household chemicals properly and use fertilizers responsibly.

Residents who want to do more can join Lexington's Adopt-a-Drain program, run in partnership with the Mystic River Watershed Association. Volunteers sign up to monitor a specific storm drain, checking it before and after heavy rain, wind or snow. The program is part of a regional effort involving 10 municipalities, funded by the Massachusetts Department of Environmental Protection. Residents can claim a drain through the program's sign-up page by typing in a nearby address and selecting an available drain on the map.

Lexington has won three "Stormy" awards from the New England Stormwater Collaborative for its green infrastructure and technology efforts, according to the town's stormwater management page. The same page notes the town faces challenges including aging infrastructure, climate change impacts and limited staffing.

With rain expected to arrive by Friday, the town's advice is straightforward: check the nearest catch basin and clear what you find before the storm hits.

Upcoming community dates: Stormwater Awareness Week continues through the week of Sept. 21. Residents can sign up for the Adopt-a-Drain program at any time through the town's website.