Temperatures will reach almost 40 C on Thursday in most parts of the Southern Interior.
In the Central Okanagan, the daytime high will be 37 C with a 30 per cent chance of showers in the late afternoon, turning to a thunderstorm.
The wind will pick up to 20 km/hr later in the day.
The North Okanagan and Shuswap will be a few degrees cooler, and residents there can also expect a thunderstorm in the early evening.
To the south, temperatures will hit 38 C with a 30 percent chance of showers, early this evening. Environment Canada is also forecasting a possible thunderstorm for the South Okanagan in the afternoon.
A heat warning is in place for the region and it will continue through to Friday, due to a ridge of high pressure over the southern interior of B.C.
Kamloops and Grand Forks will see the highest temperatures at 39 C, but with the humidity, it could feel hotter than 40 C.
Temperatures begin to drop after Friday, with Saturday and Sunday daytime highs reaching around 32 C.