Severe thunderstorm, flood watches issued for northern Illinois Friday night

10 p.m. update: A severe thunderstorm warning was issued for DeKalb, Kane, La Salle and McHenry counties effective until 11:15 p.m. Severe thunderstorm warning issued until 11 p.m. for Ogle and Lee counties.

8:10 p.m.: A severe thunderstorm watch has been issued for much of northern Illinois and is in effect until 2 a.m. Saturday, according to the National Weather Service.

Thursday and Friday’s hot and humid temperatures have given way to expected storms across the region Friday night.

The severe thunderstorm watch issued at 7:30 p.m. Friday includes Boone, Cook, Jo Daviess, Kendall, La Salle, Winnebago, Bureau, DeKalb, Kane, Lee, Putnam, Stephenson, Whiteside, Carroll, DuPage, Grundy, Kankakee, Lake, McHenry, Ogle and Will counties.

Thunderstorms with heavy rainfall is expected. Some areas could see up to 2 inches per hour of rainfall this evening.

A flood watch also is in effect until 3 a.m. Saturday for Winnebago, Boone, McHenry, Lake, Ogle, Lee, DeKalb, Kane, DuPage, La Salle, Kendall, Grundy, Kankakee, Cook, and Will counties.

Motorists should be aware that flash flooding could occur due to excessive rainfall, which could also impact creeks and streams. Underpasses also could flood.

“Flash flooding is a dangerous situation,” warned the National Weather Service. “Persons with interests along area rivers, creeks, and other waterways should monitor the latest forecasts and be prepared to take action should flooding develop.”

The NWS said residents should have multiple ways to receive weather warnings and stay tuned for further forecast updates.

A heat advisory also remains in effect until 9 p.m. Friday.

People should be aware of the symptoms of heat exhaustion and heat stroke.

The symptoms of heat exhaustion are dizziness, thirst, heavy sweating, nausea and weakness. If suffering heat exhaustion, a person needs to move to a cooler area, loosen their clothing, sip cool water and seek medical attention if symptoms don’t improve.

The symptoms of heat stroke include confusion, dizziness and becoming unconscious. If suffering heat exhaustion, call 911, move to a cooler area, loosen clothing and remove extra layers, and cool with water or ice.

Temperatures are expected to drop slightly this weekend and lead into a sunnier two days. Forecasts predict temperatures in the mid-80s to lower-80s on Saturday, and low-80s on Sunday.