Unseasonably warm weather will feel even hotter in parts of southern Ontario Thursday and Friday, thanks to the humidex.
The conditions are just right to make thunderstorms more likely as well.
Cities from Windsor to St. Catharines can expect temperatures in the mid-twenties, feeling even warmer with the humidity. Toronto will be spared the humidity Thursday, but by Friday, it could be feeling closer to 30.
And the heat and humidity will make thunderstorms more likely in all of southern Ontario.
Rob Davis, a meteorologist at The Weather Network, says the heat and humidity are the link between the thunder and lightning we may see.
"When you get rising air in a humid, sticky environment, you get thunderstorms."
Heat rising during hot, humid days is enough to force the extra moisture in the air up into thick cumulonimbus clouds. That results in rain and electrical activity in the atmosphere.
"The thunder and lightning is actually a very complicated electrical imbalance that occurs when all of this happens," Davis says.
No matter how humid it gets, though, there's usually not a guarantee of a thunderstorm.
"They have a very delicate creation process, if you will," Davis says. "I think of it more like a crock pot... where it has to brew slowly over many hours, or the conditions just have to be right to make the perfect ingredients."