Residents of 43 properties in British Columbia’s southern Interior have been told to be ready to leave on short notice as a wildfire flares nearby.

The Regional District of Okanagan Similkameen issued the evacuation alert Sunday as a 22-hectare wildfire burns northwest of Princeton.

The B.C. Wildfire Service says lightning is the suspected cause and a 29-member crew, 11 pieces of heavy equipment, helicopters and air tankers are working to contain the flames.

Story continues below advertisement

More than 40 wildfires, all of them under 25 hectares in size, are burning in the province as cool, wet weather has slowed the start of the wildfire season.

But the wildfire service reports lightning storms across the southern Interior sparked 22 new fires over the long weekend.

The wildfire danger map shows much of the southern quarter of the province is rated as high to extreme, but the majority of B.C. currently faces no more than a moderate risk.

Environment Canada is maintaining a heat warning for the north Thompson region, as temperatures are forecast to nudge 30 C, but cooler weather and rain is expected across B.C. by Thursday.

Story continues below advertisement

Our Morning Update and Evening Update newsletters are written by Globe editors, giving you a concise summary of the day’s most important headlines. Sign up today.