Long Island is in for a stretch of humid, sometimes dangerously hot days this week with the National Weather Service issuing a heat advisory for Thursday and Friday.

The advisory goes from 11 a.m. Thursday to 8 p.m. Friday. Highs those days are expected to be in the low to mid 90s with high humidity.

The weather service predicted, in an alert issued Tuesday afternoon, maximum heat indexes of between 95 and 100 degrees both days, with "minor relief" possible on Saturday. Slightly cooler temperatures are expected in eastern Suffolk, forecasters said, and thunderstorms are possible Friday afternoon and evening.

The advisory encourages those with health issues and senior citizens to avoid outdoor activities. "There is an increased risk of heat related illness for vulnerable populations with this event," the weather service said. 

After possible overnight storms, Wednesday and Thursday are forecast to be sunny, with highs in the upper 80s on Wednesday. 

The chance of storms will last through the weekend, and possibly even Monday as the high heat and humidity make conditions more prone to sudden thunderstorms.

The humidity is due to a southerly flow of wind bringing moisture from the Atlantic Ocean. 

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