CHICAGO (CBS) — Monday was expected to be a pleasantly warm summer day, but temperatures will be dangerously hot by the end of the week across the entire state.

The National Weather Service has announced a heat watch for all of Illinois from noon Thursday through 7 p.m. Friday. Temperatures were expected to reach the mid to upper 90s both days, and the heat index could reach as high as 115 each day.

CBS 2 meteorologist Megan Glaros reports the heat watch for Thursday and Friday likely will be changed to an excessive heat warning or heat advisory later in the week, depending on exactly how hot it is expected to get.

Temperatures on Thursday and Friday likely will be the hottest of the year. So far, the highest official temperature in Chicago in 2016 was on June 20, when the high was 93. Thursday’s high was expected to be about 95, and Friday’s high was expected to be about 98.

However, it doesn’t appear either day will have record-breaking heat. The record high for July 21 in Chicago is 103, set in 1901. The record high for July 22 in Chicago is 101, set in 1991.

AccuWeather meteorologist Elliot Abrams said it’s a rare July heat wave, at least for the last 16 years, when there has only been record-breaking heat on four days.

The average high for this time of year is 84 degrees in Chicago.

“All of us are going to have to watch outdoor activities in the middle to late part of the week, because temperatures are going to be in the middle to upper 90s. That’s about as hot as it ever gets. Records are close to 100, and so you can get heat stroke in a situation like this,” Abrams said.