Heat warning in effect for most of southern Ontario

(Source: Sandra Elfman)

Dangerously high temperatures will make for an uncomfortable few days in many parts of Ontario.

Environment Canada has issued a heat warning starting Monday for an area that spans from Windsor to Ottawa, and up to Sault Ste. Marie and Fort Albany.

Temperatures in the Greater Toronto Area and Ottawa could feel as hot as 45 C with the humidity by Wednesday.

Regions further north are also forecast to see humidex values of 40.

The hot air will move eastward by mid-week and will begin baking much of southern Quebec.

The Middlesex London health Unit is also warning residents to be prepared and take precautions.

Crieteria for extended heat warning

• A forecast calls for a daytime high of 31°C or higher and a forecast low of 20°C or higher for three consecutive days or longer
• A forecast calls for a Humidex of 40 or higher for three consecutive days or longer
• Forecasters anticipate that actual temperatures and humidex values in London and Middlesex County will reach the thresholds noted above.

Here's a look at the rest of the forecast

Monday:  A mix of sun and cloud. 70 per cent chance of showers late this morning and early this afternoon then 30 per ent chance of showers this afternoon. Risk of a thunderstorm late this morning and this afternoon. Wind becoming southwest 20 km/h late this morning. High 32. Humidex 40. UV index 8 or very high.

Monday Night: Partly cloudy with 30 per cent chance of showers and risk of a thunderstorm. Wind south 20 km/h gusting to 40 becoming light this evening. Low 21.

Tuesday: A mix of sun and cloud. 30 per cent chance of showers early in the morning and in the afternoon. Risk of a thunderstorm. Wind becoming south 20 km/h late in the afternoon. High 33. Humidex 42.

Wednesday: Cloudy. High 33.

Thursday: Sunny. High 33.

Friday: A mix of sun and cloud. High 31.