ST. LOUIS – A heat advisory hits the St. Louis region Sunday with heat index values expected to reach 100 for the first time this year.

Nearly 30 eastern Missouri counties and municipalities are under the heat advisory, including St. Louis City, St. Louis County and most surrounding areas. The current advisory lasts from 11 a.m. to 9 p.m. Sunday.

Temperatures will climb into the 90s on Sunday with increasing humidity. If you plan on heading outdoors, make sure to take several precautions and stay hydrated. Also consider wearing light-weight clothing and avoiding strenuous activities to prevent an increased risk of heat-related illnesses.

Dangerous heat is expected for much of the upcoming work week as well. By Monday and Tuesday, the St. Louis region could see heat index readings of 105 to 110 degrees as the actual air temperature hits around 100. Record high temperatures will likely be broken both of these days.

On Wednesday, temperatures will still be near 100 degrees and heat indices will still likely be dangerous. There is a chance of a few storms late in the day on Wednesday. Thursday and Friday will still be quite hot, but highs will drop to the lower half of the 90s.

More information: Cooling centers in the St. Louis area