Weather for New England and the Northeast

Area Forecast Discussion, National Weather Service Boston/Norton MA, 201 PM EDT Mon Aug 31 2026

**What Has Changed**

No significant changes.

**Key Messages**

1. A cool and wet start to meteorological fall. Some rain could be heavy, leading to poor drainage flooding.

2. Unsettled weather late Wednesday into Thursday, with several rounds of showers and thunderstorms. There is low confidence on the exact timing.

3. Improving weather Friday and into the holiday weekend. Other than a spot daytime shower each day, dry weather prevails with a mix of clouds and sun. Cooler than normal, with highs in the 70s and lows in the 50s, along with onshore breezes.

**Discussion**

**Key Message 1, A cool and wet start to meteorological fall**

The backdoor cold front that pushed southwest of New England this morning starts to shift back to the northeast today, bringing increasing cloud cover this afternoon. As expected over the past several days, there will be multiple rounds of beneficial rainfall this week, with the first round arriving late tonight through Tuesday.

As the frontal boundary shifts northeast, precipitable water, or PWAT, increases to between 1.8 and 2.0 inches. PWAT measures the amount of moisture available in the atmosphere if all of the water vapor were condensed into rain. This moisture will interact with a weak area of low pressure moving along the frontal boundary.

Rain is expected to arrive around midnight west of the Connecticut River Valley and around the time of the Tuesday morning commute along the I-95 corridor. BUFKIT, a tool used to examine detailed weather model soundings, shows a warm cloud layer extending to around 10,000 feet. This setup can support efficient rainfall production.

Locally heavy downpours, especially during the daytime Tuesday, are possible and could lead to localized street and poor drainage flooding. This coincides with the Day 1 and Day 2 ERO, or Excessive Rainfall Outlook, Marginal Risk, which is level 1 out of 4 for excessive rainfall.

There is expected to be a narrow area of heaviest rainfall across the southwestern portion of the forecast area. Rainfall amounts should generally range from around half an inch to 1 inch, with lesser amounts east of I-95, where totals are expected to be around a quarter inch to half an inch.

Because this rainfall will occur mainly as showers rather than steady stratiform rain, rainfall amounts can vary considerably over short distances. A subtle shift in the weather system toward the northeast could place some of the heaviest rainfall across parts of central Massachusetts and eastern Connecticut.

There is also a lower chance for thunder, mainly Tuesday afternoon, with a few hundred units of CAPE, or Convective Available Potential Energy, across mainly western Massachusetts and Connecticut. CAPE measures the amount of atmospheric energy available to thunderstorms. At this time, the overall thunderstorm risk is not considered significant.

Rain tapers off late Tuesday, with drier conditions spreading across the region Tuesday night into early Thursday morning. Given the clouds, expect a much cooler Tuesday, with highs mainly in the upper 60s to lower 70s. This will be a true reminder that meteorological fall has arrived.

**Key Message 2, Unsettled weather late Wednesday into Thursday**

High pressure, around 30.27 inches of mercury, over the Canadian Maritimes should provide dry weather for much of Wednesday, especially across eastern Massachusetts. A frontal boundary will remain to the west and southwest of Southern New England.

The front should eventually move northeast as a warm front later Wednesday and especially Wednesday night, increasing the risk for showers and thunderstorms across Southern New England late Wednesday and Wednesday night.

Wednesday will remain relatively cool, with the high pressure system and an east-southeast onshore flow limiting high temperatures to the upper 60s and lower 70s.

A trailing secondary disturbance, or short wave, along with its associated cold front, will affect the region around Thursday. There is potential for thunderstorms to become strong to severe as warmer and more humid air moves into Southern New England.

However, the more unstable air, with higher theta-e, appears likely to remain southwest of Southern New England. Theta-e, or equivalent potential temperature, is a measure meteorologists use to estimate the heat and moisture content of an air mass. This suggests that the threat for severe weather and flash flooding remains limited at this time.

Heat and humidity return Thursday as warmer air moves into the region, with highs in the lower 80s and dew points in the upper 60s and lower 70s. Dew point is a measure of how much moisture is in the air, with higher values indicating greater humidity.

**Key Message 3, Improving weather Friday and into the holiday weekend**

The weather pattern will show a definite sign of fall approaching Friday, as a strong northern weather system produces a 998 mb, or approximately 29.47 inches of mercury, maritime low late Friday into Saturday. A maritime low is a storm system that develops or strengthens near the ocean.

This will produce a cool, brisk northeast flow across Southern New England during the weekend. Highs will likely remain in the 70s, with overnight lows in the 50s.

It will feel even cooler across southeastern Massachusetts, including Cape Cod and the Islands, where northeast winds could reach 15 to 25 mph.

Cool cyclonic flow aloft, meaning air circulating around an upper-level low pressure system, will produce daytime clouds each day and possibly an isolated shower. Otherwise, dry weather should prevail.

Memorial Day Monday appears to be a typo in the original discussion given the Labor Day holiday timing. The intended reference is likely Labor Day Monday, when conditions could become warmer with less wind as a strong upper-level trough moves offshore and high pressure, around 30.27 inches of mercury, settles over Southern New England.