Long Island weather: Possible severe thunderstorms Wednesday night, Thursday, as high heat, humidity arrive in region

Severe thunderstorms may arrive late Wednesday and Thursday on Long Island, as the region transitions to a period of above-normal summerlike weather with high heat and humidity predicted, starting Sunday.

There is a chance for scattered severe thunderstorms Thursday afternoon and evening that may bring damaging wind gusts of 58 mph along with heavy rain, frequent lightning, and small hail, weather service forecasters said. An isolated tornado is possible, forecasters said.

"Generally the farther west you are, there's a somewhat better chance that there will be" stormy conditions, said meteorologist John Cristantello with the weather service's Upton office. "It's probably more likely to occur in the later afternoon hours into the early evening."

The storms Thursday will accompany temperatures at or close to 90 degrees in some parts of the island, as well as high humidity. The weather service forecasts temperatures around 85 in Islip.

"It's normally upper 70s" Cristantello said of temperatures recorded at Islip time of the year. Due to the humidity, he added, the air across the island will feel "around five degrees warmer than the actual temperature."

The highs will remain in the mid to high 80s through the weekend. Then, more intense heat — temperatures above 90 and oppressive humidity — arrives Sunday and may stay through most of the week, the weather service said.

"The potential for several days of high heat and humidity is increasing for Sunday into early next week. Heat indices could reach the mid 90s starting on Sunday and potentially exceed 100F away from south and east coastal areas into next week Monday through Wednesday," the National Weather Service said in a Wednesday advisory.

Heat indices mean how temperatures feel, when combined with humidity.

A heat wave constitutes actual temperatures reaching 90 degrees or higher for three consecutive days. It is possible Monday, Tuesday and Wednesday mark the first heat wave of 2025 in some areas, according to Cristantello.

"When you get north of the LIE, there's better chances where all three days could be above 90," he added.

Service meteorologist Dave Radell said that as of Tuesday, Long Island has received only 16.9 inches of rain since Jan. 1 — 4.25 inches less than the 21.2 inches we should have at this time. 

Despite May receiving 1.39 inches of above-average rainfall, June is registering a rain deficit, with a total amount as of Tuesday is 1.22 inches. 

Radell said June should have received should be 2.4 inches by now. 

"That gives you a sense of how much we've been lacking so far," Radell said. 

Friday and Saturday will be calm and in the mid to high 80s.

Radell said this will be the first completely dry weekend on Long Island since May 10. 

Newsday's Maureen Mullarkey contributed to this story.