A heat warning is now in effect for Toronto and most of the GTA, with several days of sweltering temperatures in the forecast.

According to Environment Canada, the heat is expected to settle in tomorrow.

“A hot and humid air mass is forecast to reach the area Monday and remain in place into Wednesday,” the weather agency said in its warning. “Maximum afternoon temperatures are expected to reach 31 degrees with humidex values around 40.”

Overnight low temperatures are expected to be in the low 20s, providing little relief from the heat.

Environment Canada is encouraging people to stay well-hydrated by drinking plenty of water.

Older adults, young children, pregnant women, those who work outside and people with chronic illnesses are among those who are most at risk from the extended heat.

People are also being reminded not to leave children or pets inside parked vehicles.

While the hot air mass is only expected to move in Monday, the city is already feeling the heat. A high of 28 C was forecast for Sunday, but the temperature was expected to feel more like 35 with the humidex.

On Monday, a high of 31 C is expected, however it could feel as hot as 41 with the humidex. The UV index will also be eight, or very high.

Along with the heat Monday, there’s a 40 per cent chance of showers in the afternoon and a risk of a thunderstorm.

Tuesday is expected to be sunny with a high of 32 C, while a high of 29 C is expected on Wednesday.

Temperatures re 4expected to return to normal on Thursday, with an expected high of 23 C.