**Summary**

Summerlike heat is surging into New England today and Wednesday with many areas across southern New Hampshire and interior Maine climbing into the upper 80s and lower 90s. Humid nights will also develop with overnight temperatures staying close to 70 degrees in some locations. Along with the heat, there is an increasing risk for strong to severe thunderstorms this afternoon and evening, especially across southern New Hampshire where damaging wind gusts and hail are possible. Cooler and much drier air arrives for the second half of the week before another unsettled weather pattern potentially develops over the weekend into early next week.

**What this means for you**

Today will feel more like mid summer than May with hot temperatures and increasing humidity across much of the region. If you have outdoor plans, stay hydrated and take breaks from the heat, especially during the afternoon. There is also the possibility of isolated severe thunderstorms later today, mainly in southern New Hampshire, capable of producing damaging wind gusts and hail. Most areas remain dry much of the day, but any storm that develops could intensify quickly. Cooler and more comfortable weather returns later this week before rain chances increase again over the weekend.

Area Forecast Discussion

National Weather Service Gray ME
Issued 650 AM EDT Tuesday, May 19, 2026

**What Has Changed**

Refreshing the aviation discussion for the 8 AM EDT TAFs.

**Key Messages**

1. Hot, well above normal temperatures move into the region today and Wednesday. Widespread highs in the upper 80s to lower 90s are expected today, with warm overnight lows in the upper 60s to around 70 degrees. Another round of hot temperatures is possible Wednesday, mainly focused from the interior to the coast.

2. An approaching cold front will bring chances for thunderstorms today and chances for showers and storms Wednesday when the front crosses. Any thunderstorm that develops this afternoon will have the potential to become severe.

3. The second half of the week will feature cooler temperatures and drier conditions. Unsettled weather is possible this weekend.

**Discussion**

**Key Message 1 Description**

Not much has changed regarding the hot temperatures expected today and tomorrow. Any lingering fog over the coastal areas or interior valleys should dissipate early this morning, leading to mostly sunny skies and strong heating through the day. Temperatures will rise quickly into the upper 80s and lower 90s across southern New Hampshire and portions of interior Maine.

The Heat Advisory for Hillsborough and interior Rockingham Counties remains on track with no major changes expected. Humidity levels are somewhat limited, so the heat index, what the temperature actually feels like to the human body, will mainly approach 95 degrees in some spots. Even so, this is a major jump from the cooler weather experienced through much of the spring season.

Tonight will remain unusually warm as southwest winds continue ahead of an approaching cold front. Overnight lows may only fall into the upper 60s and lower 70s across southern areas.

Wednesday will stay quite warm, although slightly cooler than today. Southern New Hampshire along with interior and coastal Maine should still see highs in the middle 80s to around 90 degrees. Areas near and north of the mountains will cool off somewhat behind the front, with highs generally in the lower 70s to lower 80s.

**Key Message 2 Description**

The setup for severe weather this afternoon has become a bit more concerning, especially across southern New Hampshire.

A ridge of high pressure in the middle and upper levels of the atmosphere will weaken slightly through the day while a weak area of low pressure moves across Maine. This will drag a surface trough, an elongated zone of lower pressure, across the region and could help spark isolated showers and thunderstorms during the afternoon.

Most locations are expected to stay dry because large scale atmospheric forcing remains limited. However, southern New Hampshire may see a better opportunity for storm development as a compact shortwave, a small disturbance in the upper atmosphere, moves east from Vermont and provides additional lift for thunderstorm growth.

Some high resolution computer models, known as CAMs (Convective Allowing Models), suggest a cluster of thunderstorms could form over southern Vermont during the early afternoon before moving into southern New Hampshire later in the day.

Forecast soundings from the NAM Nest model indicate an unstable atmosphere with MLCAPE values between 1500 and 2000 joules per kilogram. MLCAPE, or Mixed Layer Convective Available Potential Energy, measures how much fuel is available for thunderstorms. Forecasts also show 30 to 35 knots of deep layer wind shear through the lowest 6 kilometers of the atmosphere, which helps storms organize and strengthen.

This combination could support organized multicell thunderstorm clusters or even temporary supercell thunderstorms capable of producing damaging wind gusts up to 60 mph and hail.

Forecast SHIP values, which stands for Significant Hail Parameter, remain just under 1. That suggests the risk for extremely large hail is fairly low, but hail up to ping pong ball size could still occur if stronger rotating storm structures develop.

The tornado threat currently appears low because low level wind shear remains weak.

Across the rest of the forecast area, some storms could still become briefly strong or marginally severe, although atmospheric instability decreases farther north and east. Thunderstorms should weaken this evening after daytime heating fades, although a few showers may continue overnight near the mountains.

The cold front will move through much of the area Wednesday morning. Thunderstorms Wednesday should mainly stay focused along and ahead of the front, especially south of the mountains. A stronger storm or two cannot be ruled out across interior or southeastern New Hampshire before the front pushes offshore, but the overall severe weather threat currently appears limited.

**Key Message 3 Description**

High pressure building in from the west will bring cooler and drier conditions for the second half of the week. This weather pattern should keep more active storm systems south of New England for a time.

Attention then turns to the weekend when another area of low pressure may move toward the region and bring a steadier rainfall. Forecast confidence on timing remains somewhat uncertain. Some forecast guidance brings unsettled weather into the region Sunday, while other solutions delay the rain until Monday.

Temperatures later this week and into the weekend will feel much cooler, with daytime highs mostly in the 60s and overnight lows in the lower 40s.

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