VANCOUVER -- The BC Wildfire Service says a fire burning in British Columbia's southern Interior doubled in size over a 24-hour period to about 2.5 square kilometres.

More than 100 people, supported by aircraft and heavy equipment, are battling the blaze that broke out Aug. 4 north of Oliver.

The fire activity had calmed late Monday, but that could change as Environment Canada forecasts the heat will remain in the low- to mid-30s through the week, with no rain forecast until Saturday.

An evacuation alert prompted by the fire was issued Monday by the Regional District of Okanagan-Similkameen which covers 206 properties north of Oliver.

Steep and rocky terrain is complicating firefighting efforts and the wildfire service says a structure protection specialist and incident management team are at the scene.

Cool and damp conditions in July kept a lid on the wildfire risk across B.C.

Smoke from the fire has prompted a special air quality statement for the south Okanagan region.

Environment Canada says Penticton, Summerland, Naramata, Oliver and Osoyoos will be being impacted by the smoke from the wildfire over the next day or two.

The statement says people with health conditions, the elderly, pregnant woman or infants are more likely to experience health effects from exposure to the smoke.

The wildfire service says a suspected lightning-caused blaze discovered Sunday in northwestern B.C., has already charred 44 square kilometres of timber west of Telegraph Creek.

No structures are threatened and the flames are believed to be spreading slowly to the east, but a social media post from the service says smoke is highly visible in Telegraph Creek, nearly 50 kilometres to the east.

Twenty-one homes in that community were destroyed by a wildfire last year that razed more than 12-hundred square kilometres of bush and forced an evacuation that continued for 102 days.

The wildfire service still lists that blaze as a "wildfire of note" because of extreme drought conditions in the region and the potential for flames that smouldered underground over the winter to erupt again as another hot spell arrives.

Anyone conducting activity in the Cassiar Fire Zone, which includes the area west of Telegraph Creek where the current large blaze is burning, should use extreme caution, says the online post from the wildfire service.

Just under 600 wildfires have been recorded in B.C. since the wildfire season began on April 1, with 29 currently active.

This time last year, there had been 1,468 fires recorded across the province, the fire service says.

The service says 57 per cent of the 2019 wildfires were human-caused, while lightening is blamed for the remainder.