High heat across southern Manitoba and northwestern Ontario could cause health problems for some people on Wednesday.

Environment Canada issued heat warnings for the regions Wednesday morning. The day will be hot and humid, with humidex values reaching close to 40 Celsius.

The hot air could produce thunderstorms in the afternoon and into the evening.

Night time won’t bring much relief, either, as the temperature will only fall to about 20 C by Thursday morning, Environment Canada said. On Thursday, the daytime high will rise to around 30 C, although humidity levels will be significantly lower, Environment Canada said.

The high temperatures could cause heat stroke or heat exhaustion.

People at risk of health problems due to the heat include older adults, people with chronic illnesses, people who work or exercise in the heat, homeless people and people without access to air conditioning.

Environment Canada advises people to drink plenty of liquid, and not to wait until you already feel thirsty before drinking.

For more information, visit Manitoba Health’s website.