Boston is beginning Monday, Sept. 21, under clouds and patchy fog before skies brighten later in the day. The high is expected to reach about 64 degrees, with northeast winds of 10 to 14 mph, according to the National Weather Service.
A cool, increasingly breezy week
The National Weather Service Boston/Norton office expects patchy fog to lift early Monday, with any lingering light showers over eastern Massachusetts moving offshore by late morning. Monday night should remain mostly cloudy, with temperatures falling to around 54 degrees and northeast winds continuing.
Tuesday through Thursday are expected to stay cool and breezy. The more unsettled part of the forecast arrives late in the week, when rain chances increase and winds could strengthen as a slow-moving coastal low develops near the region.
The coastal low remains uncertain
Forecasters are monitoring the system for possible rain, stronger winds and coastal impacts, but its track and strength remain uncertain. Boston could experience gusty conditions, while rough seas, coastal erosion and flooding risks would generally be greatest closer to the coast and over the waters, according to the Boston/Norton forecast discussion.
No land-based watch or warning for Massachusetts is identified in the material reviewed here. That status does not establish that flooding or other land impacts are impossible; it reflects the forecast uncertainty and should not be read as a definitive all-clear.
Boston’s longer-term coastal exposure
The possible late-week system is separate from Boston’s longer-term coastal-risk planning. The City of Boston says it has completed coastal-resilience plans addressing sea-level rise and storm-related flooding along all 47 miles of the city’s coastline. City records also say about one-sixth of Boston sits on landfill, contributing to vulnerability to sea-level rise and coastal flooding.
The National Oceanic and Atmospheric Administration reports that high-tide flooding is becoming increasingly common as sea levels rise, with climate change contributing to that rise. That is a documented background trend, not evidence that this week’s coastal low will produce flooding in a particular Boston neighborhood.
A recent comparison, with limits
On Sept. 15–16, 2023, Hurricane Lee tracked well offshore of southern New England, according to the National Weather Service Boston/Norton post-storm summary. Its main effects were on Cape Cod and the Islands, including 50-to-60-mph wind gusts, heavy rain, minor coastal flooding, hazardous marine conditions, coastal erosion and rip currents.
Lee is useful only as an example of how a system tracking offshore can still affect coastal and marine areas. It was a hurricane, while the system now being monitored is an uncertain coastal low, so the 2023 event does not establish what Boston will experience this week.
