The National Weather Service has extended its heat advisory for Fishers and the rest of central Indiana, with dangerous heat and humidity now expected to last through Friday evening.

The advisory is in effect until 8 p.m. Friday. Forecasters say peak heat index values — a measure combining temperature and humidity to reflect how hot the air actually feels — will run between 100 and 108 degrees. The advisory covers all of central Indiana, including Hamilton County.

“Hot temperatures and high humidity may cause heat illnesses,” the weather service said in its advisory.

The agency urges residents to drink plenty of fluids, limit time outdoors and check on relatives and neighbors. Older adults, young children and people who work or exercise outdoors face the greatest risk during stretches of high heat.

Storms are also in the picture. The weather service says an isolated thunderstorm cannot be ruled out Wednesday afternoon and evening. Thunderstorms are possible at times from Thursday night through Saturday night for all or part of the region, according to the agency’s hazardous weather outlook.

Heat index values in the 100-to-108 range are expected to peak in the afternoon and early evening hours each day the advisory remains in effect, which covers the window when many outdoor activities, practices and construction work take place across Fishers.