Environment Canada has issued its first heat warning of the summer for the Greater Toronto Area.

The weather agency issued the warning late Friday morning saying that the GTA and most of southern Ontario should expect high daytime temperatures “with humidex values near 40.”

“A hot and humid airmass is expected to remain in place into Saturday,” the warning said.

“On Saturday temperatures will remain near thirty with humidex values in the upper thirties; however with the passage of a cold front, cooler temperatures and lower humidity is expected for the remainder of the weekend.”

Environment Canada is forecasting a daytime high of 31 degrees on Friday, feeling like 41 degrees with the humidex.

There is a 60 per cent change of showers in the afternoon with a risk of a thunderstorm.

On Saturday, residents can expect a mix of sun and cloud with a 60 per cent change of showers in the early morning and a 40 per cent chance of rain throughout the day.

However, the temperatures are still expected to be scorching, with a high of 29 degrees, feeling like 39 degrees with the humidex.

In the heat warning, Environment Canada urged residents to “drink plenty of water” and to stay in cool places if possible.

“Heat warnings are issued when very high temperature or humidity conditions are expected to pose an elevated risk of heat illnesses, such as heat stroke or heat exhaustion,” the warning said.

“The risks are greater for young children, pregnant women, older adults, people with chronic illnesses and people working or exercising outdoors.”