Significant Weather Blog: Thursday, October 9, 2025 6 PM

WIDESPREAD FROST/FREEZE TONIGHT

RISK OF COASTAL FLOODING AND BEACH EROSION ALONG PORTIONS OF THE MASSACHUSETTS COAST SUNDAY AND ESPECIALLY MONDAY

Freeze/Frost Tonight

Temperatures will drop to near or a little below freezing late tonight and early Friday morning for most of interior southern New England.  Closer to the coast, there’s a high risk of frost just back from the immediate shoreline.  Temperatures tonight will effectively end the growing season for most of southern New England.  A Freeze Warning is in effect for most of interior southern New England.  Surface high pressure moving over the area will provide excellent radiational cooling under clear skies and light winds tonight, and temperatures across interior southern New England will drop into the upper 20s and lower 30s overnight.  This is expected to be the area’s first widespread frost/freeze event.

Coastal Storm

All numerical weather prediction global models, including both operational and ensemble runs, depict surface low pressure development off the North Carolina coast by the weekend and move the system far enough north to have at least some impact on southern New England.  All the models (and their ensembles) depict this system becoming vertically deep from the lower to upper troposphere and hence cause it to stall or slowly meander.  There remain differences in details among the models, however, especially on intensity, exact track, and how long it may stall off the U.S. east coast.

For southern New England, this system will bring wind, rain, and coastal impacts, although there remains uncertainty in the extent and severity.  There could be some impacts from this system through mid-week.  Here’s a look at potential impacts:

Wind:  East to northeast winds will increase Sunday and probably peak late Sunday night into Monday.  Over the Cape and Islands, gusts to 40 mph are likely by mid or late Sunday afternoon and increasing to 50 to 55 mph Sunday night into Monday.  Along the Massachusetts east coast north of Cape Cod, east to northeast wind gusts may reach 45 to 50 mph late Sunday night through Monday.  Scattered tree damage is possible in coastal areas.  The strong winds will result from what will be a tight pressure gradient between the low pressure center just offshore and a relatively strong high pressure center anchored over the Canadian Maritimes.

Coastal Impacts:  The strong onshore wind will cause areas of coastal flooding and beach erosion along much of the United States east coast.  Although the greatest impact may be along the North Carolina outer banks and the Delaware/Maryland open coast, erosion and coastal flooding may be an issue further north to southeast New England as well.

More specifically for southeast New England, the increase in onshore east to northeast winds may occur sufficiently soon to produce a storm surge of 1 to 2 feet and waves to 10 feet along east and southeast facing ocean shorelines of the Cape and Islands by the time of the mid to late Sunday afternoon high tide, which is fairly high astronomically to begin with.  This may cause pockets of coastal flooding and some erosion.  The storm surge will likely build to between 2 and 3 feet all along the Massachusetts east coast (including the Cape and Islands), and near shore waves may build to 15 to 20 feet during Monday.  The early Monday morning high tide is not particularly high and so the impact then may be fairly minor.  The higher high tide late afternoon/early evening on Monday may be more problematic with areas of minor to possibly moderate coastal flooding along vulnerable areas of the Massachusetts east coast from Newburyport/Plum Island to the Cape and Islands.  The relatively long duration of elevated water levels and significant wave action will likely cause beach erosion along vulnerable reaches of the Massachusetts east facing shorelines including Nantucket, Martha’s Vineyard, the ocean side of the outer Cape, Plymouth County coast, and the shoreline from Cape Ann to Plum Island.  Some erosion may persist even into Tuesday depending just where and how long the storm remains in the vicinity.  It is too soon to have a good handle on the severity.  As noted in the previous blog, we are fortunate that this system isn’t occurring now when the astronomical high tides are especially high (period of “King Tides” with the gravitational pull of the Moon and Sun acting in conjunction).

Rain:  The extent, duration, and amount of rain is highly sensitive to the exact track of the storm and thus remains rather uncertain.  A consensus of models suggest rain reaching the south coast of New England sometime mid to late Sunday afternoon and spreading across most, if not all, of southern New England Sunday night into Monday morning.  Some models track the low pressure center such that the rain persists all of Monday into at least Monday night whereas other models curl the low center back to the southwest and cause an end or at least a break in the rain Monday afternoon.  Although uncertain as to how much, it looks like the heaviest rain will probably fall across CT and RI, and southeast MA, but this is subject to change.

Marine:  This coastal storm will likely have a very significant marine impact given the strength of surface winds and the duration.  Gale to Storm Force winds are possible across the southern New England coastal waters, strongest east and south of the Cape and Islands late Sunday through Monday.  Waves may build late Sunday night and Monday to 15 to 20 feet across the eastern Massachusetts near shore waters exposed to the open ocean and even higher between 20 and 25 feet offshore to the south and southeast of the Islands.  Ferry service to Block Island, Martha’s Vineyard, and Nantucket may be affected Sunday afternoon through Monday.  Travelers to any of the islands should check with the appropriate ferry office.

Next Message

Will continue to monitor and likely update this message once more on Friday.

About this Blog and Disclaimer

The National Weather Service monitors the weather 24/7 and updates forecasts, watches, and warnings as necessary.  For most of southern New England, refer to your local Weather Forecast Office for the latest forecast/warning information at weather.gov/box.  For information from other Weather Forecast Offices, go to weather.gov and click on the location of interest on the map.  For the latest information on Atlantic basin hurricane activity, access the National Hurricane Center website at nhc.noaa.gov.

A blog is issued when there is a potential risk of hazardous weather to southern New England and serve to provide background information regarding the significant weather with somewhat of an educational slant.  In the case of hurricanes, the author will attempt to issue a message when any portion of the United States coastline may be seriously impacted.  It’s intended to complement and not serve as an alternative to official forecasts issued by the National Weather Service.  Readers are urged to check National Weather Service forecasts and warnings for the most timely and updated weather information.  This weather message is solely produced by the listed author and does not constitute an official product of the Blue Hill Observatory and Science Center (BHOSC).

The frequency of this blog will depend upon the nature of the weather threat and availability of the author.  Thus, for the latest information on weather forecasts and warnings, refer to the National Weather Service, which monitors and forecasts the weather 24/7.

Blue Hill Observatory and Science Center (BHOSC)

The BHOSC maintains a continuous daily observation record that dates from February 1, 1885 without interruption and provides educational information on weather and climate to area students and the community at large.  Your support of BHOSC is much appreciated and enables this nonprofit organization to maintain the long-term climate record at the Blue Hill Observatory (longest continuous record in North America) and provide valuable educational resources on weather and climate via outreach to schools, site visits/tours, webinars, and conferences.  For more information on the Blue Hill Observatory and Science Center, explore bluehill.org.

Southern New England Weather Conference

If you are reading this message, then you probably have an interest in the weather and/or climate of our region.  Consider signing up for the Southern New England Weather Conference to be held Saturday October 25 at the Meditech facility in Canton.  There is a fascinating slate of prominent speakers lined up! Go to bluehill.org to register.

Message issued October 9, 2025 by:
Bob Thompson
Retired National Weather Service Meteorologist
Blue Hill Observtory and Science Center Board member