A heat advisory is in effect through Friday for the entire city.

Heat index values up to 101 degrees are expected today and tomorrow. The National Weather Service says it may extend the advisory into Saturday. A heat advisory is issued when the combination of heat and humidity is expected to make it feel like 95 to 99 degrees for two or more consecutive days, or 100 to 104 degrees for any length of time.

Seniors and those with chronic health problems or mental health conditions are at an increased risk. Homes without air conditioning can be much hotter than outdoor temperatures.

Tonight stays warm and muggy under partly cloudy skies, with temperatures only dropping into the upper 70s across the boroughs. Friday gets off to a steamy start with a mix of sun and clouds as oppressive heat and thick humidity settle over the Bronx and Brooklyn.

Daytime highs will climb around 90 degrees, pushing real-feel heat index values well into the upper 90s to near 100. Thunderstorm chances increase significantly heading into the afternoon, with scattered pop-up cells possible as early as 2 p.m. and the highest coverage expected after 4 p.m. Any storm that hits could bring heavy downpours, gusty winds, and localized street flooding. Friday night remains sticky and muggy with a lingering shower possible as temperatures hold near 75 to 78 degrees.

Classic midsummer heat continues through the weekend with a mix of sun and clouds on both Saturday and Sunday. Highs will hover around 90 degrees, but persistent humidity will keep peak feel-like temperatures in the middle to upper 90s. A few strong isolated thunderstorms could pop up Saturday afternoon, especially after 3 p.m., while Sunday looks drier with a lower risk for rain, making it the pick of the weekend for outdoor plans, whether heading to Coney Island, relaxing in Prospect Park or spending time along the waterfront.