Dangerously hot conditions have prompted the National Weather Service in Indianapolis to issue an Extreme Heat Warning covering a large swath of Indiana, including Fishers and the rest of Hamilton County. The warning remains in effect until 8 p.m. EDT Thursday.

Forecasters say heat index values — a measure of how hot it actually feels when humidity is factored in — could climb as high as 109 degrees. The warning stretches across portions of central, east central, north central, south central, southeast, southwest, and west central Indiana.

“Heat related illnesses increase significantly during extreme heat and high humidity events,” the Weather Service said, urging residents to take the conditions seriously. Officials recommend drinking plenty of fluids, staying in air-conditioned spaces, avoiding the sun, and checking up on relatives and neighbors who may be vulnerable to the heat.

Hamilton County Emergency Management Urges Caution

Hamilton County has been upgraded to an Extreme Heat Warning that runs until 8 p.m. Thursday. With heat index values potentially reaching 109 degrees, county emergency management officials are echoing the call to drink plenty of water, stay in air-conditioned spaces, avoid the sun, and check on loved ones.

For those staying indoors, officials offered several tips to keep cool: keep blinds or curtains closed to block out the sun, use fans or portable air conditioners to improve circulation, and wear light, breathable clothing while cooling down with damp cloths.

Emergency management also recognized that not everyone has the option of staying inside. For those who must be outdoors, officials advise planning outdoor time for the early morning or evening when temperatures are cooler, taking frequent breaks in shaded or cooled areas, and carrying water or electrolyte drinks to sip often. Residents are reminded to never leave children, older adults, or pets in parked cars.

Know the Signs of Heat Illness

Officials are urging everyone to stay alert for signs of heat illness, which can include headache, faintness, nausea, dizziness, or cramps. Anyone experiencing these symptoms should move to a cooler area and hydrate. Call 911 if needed.