Weather for New England and the Northeast

**Area Forecast Discussion, National Weather Service Gray ME**
**632 AM EDT Tuesday June 30 2026**

**What Has Changed**

For this update, the latest observations have been blended into the forecast and the aviation discussion has been updated. No major forecast changes were needed.

**Key Messages**

1. Heat and oppressive humidity arrive Wednesday and last through at least Friday, possibly into Saturday. All air conditioner installations and heat preparations should be completed by today.

2. Starting late today through the end of the week, the atmosphere will have the necessary ingredients for thunderstorms, some of which could become strong to severe. The Storm Prediction Center continues a Marginal Risk for severe storms late today and again Wednesday.

**Discussion**

**Key Message 1 Description**

Today will be very warm, with afternoon high temperatures in the 80s to lower 90s. Dew points, a measure of how much moisture is in the air, will generally remain in the 50s except along the coast. There, onshore winds from the ocean will raise dew points into the 60s while keeping temperatures somewhat cooler. As a result, the heat index, or feels like temperature, will remain close to the actual air temperature today.

Beginning Wednesday, a large area of high pressure centered over the Ohio Valley will expand into New England, bringing much hotter and much more humid conditions. Temperatures several thousand feet above the ground are forecast to exceed 68 degrees, a strong indicator that afternoon highs could climb into the middle and upper 90s. Coastal communities should receive some relief from ocean breezes during the afternoon.

Dew points are expected to rise into the lower and middle 70s, creating dangerous heat index values between 105 and 110 degrees across areas included in the Extreme Heat Watch, with widespread feels like temperatures in the 90s elsewhere.

There remains uncertainty regarding the timing and coverage of thunderstorms from late today through the end of the week. Thunderstorms could temporarily lower temperatures while increasing humidity behind them. Additional details are discussed below.

Thursday continues to appear to be the hottest day of the week. Temperatures several thousand feet above the ground are forecast between 72 and 73 degrees, supporting afternoon highs around 100 degrees across much of the interior, especially southern New Hampshire. It remains uncertain whether a cooling sea breeze will develop along the coast, and that will also depend on thunderstorm activity. Dew points are again expected in the lower and middle 70s, pushing heat index values close to 110 degrees wherever temperatures reach the upper 90s or around 100 degrees.

The heat and humidity are expected to continue through Friday and possibly Saturday, although temperatures should gradually begin to ease. By Sunday, forecast models agree that a dip in the jet stream moving across Atlantic Canada will allow somewhat cooler air to move into the region. Even so, afternoon highs are still expected to reach the lower 90s across southwest Maine and southern New Hampshire.

Nighttime temperatures will also remain unusually warm through Friday night. Without thunderstorms, overnight lows will likely only fall into the middle and upper 70s across southern and central areas. If thunderstorms develop, temperatures could briefly drop into the upper 60s or lower 70s. The forecast reflects a compromise between these possibilities. In the Merrimack River Valley, overnight temperatures around 80 degrees are possible Wednesday and Thursday nights if storms do not develop.

**Key Message 2 Description**

Several rounds of thunderstorms are possible beginning late today and continuing through the end of the week. Confidence remains low regarding the exact timing and locations, especially after Wednesday.

The atmosphere is expected to have ample instability, measured by CAPE (Convective Available Potential Energy), which represents the fuel available for thunderstorms. Wind shear, the change in wind speed and direction with height, will also be sufficient to support stronger storms. However, the dominant area of high pressure will limit the large scale lifting normally needed to trigger widespread thunderstorm development.

High resolution forecast models, known as CAMs (Convection Allowing Models), continue to suggest one or two organized thunderstorm complexes, known as MCSs (Mesoscale Convective Systems), could develop upstream and move into the Northeast. One may arrive late today into tonight, with another possible on Wednesday or Wednesday night. Forecast guidance varies considerably, with some solutions keeping the strongest storms over New York and Vermont.

The Storm Prediction Center has placed much of the area under a Marginal Risk for severe thunderstorms today, with a Slight Risk just west across New York and Vermont. Forecasters will closely monitor whether an organized thunderstorm complex develops and tracks into New Hampshire this evening, as it could produce damaging wind gusts.

Another Marginal Risk remains in place for Wednesday as another organized thunderstorm complex or smaller disturbance generated by earlier storms approaches the Northeast.

Outside of these organized systems, isolated thunderstorms could still develop over the mountains or along sea breeze boundaries during the afternoon, although current forecast models do not show a strong signal for widespread development.

The combination of persistent heat and high humidity will continue providing energy for thunderstorms through Thursday and into the weekend.
Conditions may become more favorable for thunderstorm development by Saturday into Sunday as the upper level weather pattern becomes more supportive, although details remain uncertain at this time.