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Here’s how this heat wave will end — with a cold front and thunderstorms

High heat and humidity have been blanketing the region since last week and are expected to linger one more day.Erin Clark for the Boston Globe

High heat and humidity have been blanketing the region since last week and are expected to linger one more day. But the icky weather is going to break Friday. Here’s how it’s going to come to an end — and what it means for your weekend.

The National Weather Service says a cold front will pass through with showers and thunderstorms, some of which might contain gusty winds and torrential rainfall. Seasonable temperatures and lower humidity are expected to follow over a beautiful weekend.

Thursday, of course, will be stifling with temperatures in the 90s, and Thursday night will be muggy and uncomfortable with low temperatures in the mid- to low 70s, forecasters said.

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But on Friday, thunderstorms running along and ahead of the cold front will arrive in Western Massachusetts around sunrise and sweep across the state from west to east, arriving in the Boston area any time from 11 a.m. to about 4 p.m. and rolling out over Cape Cod by 5 p.m., National Weather meteorologist Frank Nocera said.

“It’s looking like an early show,” he said, compared with the common pattern of thunderstorms arriving in Boston later in the day.

The weather service is concerned some of the storms might bring heavy rain that could cause localized flash flooding. Forecasters issued a flash flood watch effective from early Friday morning through Friday afternoon.

Temperatures and humidity will drop in the afternoon and evening after the storms roll through. The temperatures Saturday morning in Boston may well drop to 60 degrees, Nocera said.

West of Boston, lows may get into the 50s. There will be “almost a touch of fall in some of the distant suburbs,” Nocera said, noting that the temperature in the town of Orange could drop to 49 degrees.

“From time to time, we do have these refreshing Canadian air masses. The jet stream dips down and breaks the heat wave. So that’s what’s going to happen,” he said.

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High temperatures Saturday will be 75 to 80 in the Boston area. On Sunday, the highs will be in the upper 70s to lower 80s, with comfortable humidity. On Monday, the temperature is expected to rise to around 85, still with comfortable humidity, Nocera said.

High temperatures are expected to remain near average, which is around the low 80s, through the week, Nocera said.

But temperatures could start climbing again late next week, forecasters said in a discussion posted on the Web.