Weather for New England and the Northeast

**Area Forecast Discussion, National Weather Service Boston/Norton MA,
150 PM EDT Tuesday, September 1, 2026**

**WHAT HAS CHANGED**

Rainfall totals have been increased slightly for today, with the Connecticut River Valley likely receiving the highest amounts. Otherwise, Wednesday looks cloudy and generally dry, followed by an increasing chance for showers and possibly a few severe thunderstorms Thursday.

**KEY MESSAGES**

Widespread rain today, possibly heavy at times. There is a concern for localized urban and poor-drainage flooding.

Cloudy but drier Wednesday, with shower chances decreasing. Precipitation chances return Thursday, with an increasing chance for showers and thunderstorms throughout the day.

Improving weather Friday and into the holiday weekend. Other than an occasional afternoon shower each day, dry weather should prevail with a mix of clouds and sunshine. Temperatures will be cooler than normal, with highs in the 70s and lows in the 50s, along with onshore breezes.

**DISCUSSION**

**KEY MESSAGE 1, Widespread rain today**

Rain continues to spread across the region today and will likely reach the I-95 corridor. Radar shows areas of heavier rainfall along and ahead of a warm front, which will bring a more moisture-rich air mass into the region. The increased moisture is described technically as higher theta-e, or equivalent potential temperature, which is a measure of how warm and moist the air mass is.

There will be enough low-level convergence, where air is coming together near the surface, to produce bands of heavier precipitation and locally heavy rainfall through much of today. Computer forecast models known as CAMs, or convection-allowing models, show the greatest risk for heavy rain across portions of central Massachusetts and Connecticut.

BUFKIT forecast soundings, which provide a detailed look at the atmosphere at different levels, show warm-cloud depths increasing to 10,000 to 12,000 feet southwest of the warm front. This setup favors efficient rainfall production.

The HREF, or High-Resolution Ensemble Forecast system, shows a 10 to 30 percent probability of at least 1 inch of precipitation in 3 hours across these same areas. This corridor therefore has the greatest risk for isolated urban and poor-drainage flooding.

Farther northeast, cooler stratiform rain processes, meaning widespread steady rain rather than showers developing from individual areas of rising air, will be more dominant. Rainfall rates should therefore be lighter.

Rainfall totals are expected to be around one half inch to 1 inch, with locally higher amounts of 1.5 to 3 inches southwest of I-95. Farther northeast, totals should generally range from one quarter inch to one half inch. Because much of the rain will come from showers rather than steady stratiform rain, rainfall amounts could vary considerably over relatively short distances.

There is also a lower chance for thunder, mainly Tuesday afternoon. A few hundred J/kg of CAPE, or Convective Available Potential Energy, will be present mainly across western Massachusetts and Connecticut. This represents some atmospheric instability, but the overall severe weather threat today is not significant.

Rain will taper off from west to east this afternoon, with drier conditions spreading across the region overnight. There could be some lingering drizzle and light showers, but these should be the exception rather than the rule.

With extensive cloud cover, today will be much cooler, with highs mainly in the upper 60s to lower 70s, a true reminder that meteorological fall has arrived.

**KEY MESSAGE 2, Drier Wednesday, more active Thursday**

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

This front will eventually move northeast as a warm front Wednesday and especially Wednesday night, increasing the risk for showers and thunderstorms across southern New England late Wednesday and Wednesday night.

Wednesday will remain cool, with the high pressure system and an easterly to southeasterly onshore flow limiting high temperatures to the upper 60s and lower 70s.

A greater risk for more widespread showers and thunderstorms arrives Thursday as an upper-level disturbance and surface cold front move in from the west. Forecast guidance is becoming more consistent in showing increasing instability Thursday afternoon.

The latest NBM, or National Blend of Models, shows widespread 60 to 80 percent probabilities of CAPE exceeding 1,000 J/kg mainly along and south of the Massachusetts Turnpike Thursday afternoon. These values are higher than in previous forecasts, suggesting that the warm sector, the warmer and more humid air ahead of the cold front, may extend farther north than previously expected.

Latest probabilistic guidance from NSSL, the National Severe Storms Laboratory, and CSU, Colorado State University, also supports this trend. These forecast tools indicate a 15 percent chance of severe weather across southern New England Thursday.

Heat and humidity will return Thursday as the warmer air mass moves in, with highs in the lower 80s and dew points in the upper 60s and lower 70s. Higher dew points mean noticeably more humidity in the air.

**KEY MESSAGE 3, Improving weather Friday into the holiday weekend**

The weather pattern Friday will show a definite sign of fall approaching, with a strong northern jet-stream disturbance producing a deep maritime low pressure system, around 29.47 inches of mercury, late Friday into Saturday.

This will bring a cool, brisk northeast wind into southern New England over the weekend. High temperatures 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 air circulating around the upper-level low pressure system will produce afternoon clouds each day and perhaps an occasional shower. Otherwise, dry weather should prevail.

Warmer temperatures and lighter winds are possible on Labor Day Monday as the large upper-level trough moves offshore and high pressure, around 30.27 inches of mercury, settles over southern New England.