Weather for New England and the Northeast

**Area Forecast Discussion**
**National Weather Service Gray ME**
**250 AM EDT Sun Jun 28 2026**

**What Has Changed**

A Dense Fog Advisory has been issued through 8 AM EDT this morning for the coast and portions of western interior Maine. Otherwise, there are no significant changes with this forecast update. The primary focus continues to be the potential for extreme heat by the middle of the week.

**Key Messages**

1. Seasonable temperatures continue today with scattered showers and isolated thunderstorms this afternoon.

2. Heat and humidity will build through the middle of the week, bringing the potential for extreme heat Wednesday and Thursday across interior and coastal Maine and the southern half of New Hampshire. Prepare cooling systems early this week, and if your plans include strenuous outdoor activities, consider moving them to the morning when the heat is less intense.

**Discussion**

**Key Message 1 Description**

A broad area of cooler air circulating high in the atmosphere, known as cyclonic flow, will remain over the region through today before shifting east tonight. Daytime sunshine will once again provide enough heating to create moderate atmospheric instability, technically known as Surface Based CAPE, of around 1000 joules per kilogram across inland areas.

This unstable air, combined with the upper level weather pattern, will allow scattered showers and perhaps a few thunderstorms to develop during the afternoon. However, because there is no strong weather front or other lifting mechanism at the surface, storm coverage should remain limited.

Winds changing speed and direction with height, referred to as deep layer shear, will reach around 40 mph. That means one or two storms could become stronger than average, although widespread severe weather is not expected.

High temperatures will generally reach the middle to upper 70s across northern areas and along the coast, with lower 80s elsewhere.

Showers and any thunderstorms will fade this evening after sunset as daytime heating is lost. A light west wind overnight should keep fog mostly confined to the valleys.

**Key Message 2 Description**

Forecast ensembles, multiple computer model simulations used to measure forecast confidence, continue to indicate a period of extreme heat moving into at least south central New Hampshire and southwestern Maine Wednesday and Thursday. Hot and humid conditions could continue into Friday.

These forecast ensembles show an unusually strong upper level ridge of high pressure developing over the Northeast. At around 18,000 feet, the strength of this ridge is forecast to exceed the 99th percentile for late June, meaning it is exceptionally strong compared to what is normally observed.

The ridge will also bring unusually high moisture levels and very warm air several thousand feet above the ground. Confidence remains high for a prolonged period of heat stress from Wednesday into Friday, with daytime heat index values climbing into the 100s while overnight temperatures struggle to fall below 70 degrees.

Before the heat arrives, northwest winds aloft and high pressure will bring fair weather Monday.

Late Tuesday, low pressure moving across James Bay will push a warm front through northern New England, increasing the chances for showers and thunderstorms through Tuesday night.

Behind the warm front, temperatures several thousand feet above the ground will become unusually warm, supporting afternoon highs in the middle 90s Wednesday and approaching the lower 100s Thursday.

At the same time, dew points climbing into the 70s will create very oppressive humidity. Winds may develop an onshore component Wednesday, providing some relief along the coast. On Thursday, stronger west winds may prevent the cooling sea breeze from forming, allowing very hot temperatures to extend all the way to the coastline.

Forecast guidance continues to show heat and humidity lasting into Friday, with highs in the upper 90s and dew points remaining in the 70s. Precautions should be taken for what could become a prolonged period of dangerous heat. Forecast ensembles suggest the upper level ridge will weaken or shift west next weekend, allowing the extreme heat to gradually ease.

One factor that could keep temperatures from reaching their full potential would be thunderstorms developing along the northern edge of the upper level ridge. These storms could bring increased cloud cover along with additional chances for showers and thunderstorms.

There is also a modest signal for an **Elevated Mixed Layer (EML)** moving east from the Upper Midwest Wednesday into Wednesday night. An Elevated Mixed Layer is a layer of very warm, dry air located several thousand feet above the ground. When it moves over a hot and humid air mass, it can significantly increase atmospheric instability and raise the risk of severe thunderstorms.

If this develops, atmospheric instability, technically referred to as CAPE, could become unusually high for northern New England and support severe thunderstorms.

Machine learning guidance from **Colorado State University (CSU)** continues to show a strong signal for severe thunderstorms Wednesday and Thursday. The exact timing and locations remain uncertain and should become clearer over the next couple of days.