Heat returning to Long Island this weekend following Friday evening's thunderstorms

Thunderstorms swept through some parts of Long Island areas Friday evening, a nightcap to a sticky, sweltering afternoon, during which temperatures felt as hot as 100 degrees.

The storms were accompanied by a drop in temperatures to a much milder 73 degrees at Mac Arthur Airport in Islip just after 9 p.m., although humidity remained high. But the high temps and humidity will return Saturday, with the National Weather Service forecast painting an oppressive weather picture, with possible patchy fog and showers.

The weather service notes a 30% chance of rain and thunderstorms on Saturday, likely after 5 p.m. It will otherwise be mostly sunny, with highs in the upper 80s. Southwest winds will reach 8 to 14 mph.

A heat advisory will remain in effect through 8 p.m. Saturday, when temperatures are expected to again drop to the mid-70s after nightfall. 

Heat advisories are issued when the combination of heat and humidity is expected to make it feel like it is between 95 and 99 degrees for two or more consecutive days, or between 100 and 104 degrees for any length of time. On Friday, that combination made it feel like temperatures were in fact in the triple digits.

That combination also has the weather service warning vulnerable Long Islanders — seniors, those with chronic health problems or mental health conditions — to use air conditioning or go to a location that has air conditioning.

The weather service also advised limiting outdoor work if possible, noting the Occupational Safety and Health Administration "recommends scheduling frequent rest breaks in shaded or air-conditioned environments." Staying hydrated also is a must.

Sunday should be filled with sunshine, with a high again in the upper 80s. But despite a light breeze, the heat index could again climb into the mid-90s. 

On Friday in Islip, the temperature climbed to 89 degrees about 2 p.m., but the humidity made conditions feel like 100 degrees.

About 7:15 p.m. Friday, showers and storms were "moving through western Suffolk County," weather service meteorologist Brian Ciemnecki told Newsday. Also at that time, a thunderstorm watch for Nassau County expired.

"They should be out of here in a couple of hours," Ciemnecki said of the storms.

The conditions were forecast to bring wind gusts up to 40 mph, strong enough to break off tree limbs and scatter objects not tied down, the weather service said.

A flood advisory for Nassau and western Suffolk warned that storms could drop upwards of two inches was in effect through 9:30 p.m., according to the weather service.

The Cole Swindell summer concert at the Harry Chapin Lakeside Theater in Eisenhower Park, set to begin at 7 p.m. Friday, had been rescheduled to 8 p.m. due to the  weather system moving through the area, according to a news release from the Nassau County executive's office.

Air quality monitoring site AirNow.gov said ground-level ozone readings had been expected to surpass 100 on Friday, creating an unhealthy air quality situation for "sensitive groups," which include people with lung disease such as asthma, as well as children, teens and older adults who are routinely active outdoors for more than six hours daily. That alert covers all of Long Island, as well as the five boroughs and Westchester and Rockland counties.