Fire crews say the Jade fire burning in the Yalakom Valley near Lillooet, B.C., is becoming increasingly intense, and they are concerned that forecast wind and lightning could make it worse.

More than 100 firefighters have been battling the aggressive wildfire after it was triggered last week by a lightning strike, but it is still only about 15 per cent contained.

The fire has already spread across an estimated 670 hectares and has resulted in an evacuation alert for 85 people in 30 homes.

Fire information officer Garry Horely isn't making any predictions about what will happen when crews return on Tuesday to fight the blaze.

"Our crews are going to be very vigilant today. We are going to be on guard for the predicted thunderstorms, and we may have to move off of it, if the winds to become erratic. It will be a very dangerous situation to be out there," said Horely

Dry July causing problems

Crews have been steering the fire to the north, toward rocks, and the alpine, and the closest home is about a half-kilometre to the southwest of the fire, he said.

B.C. has been experiencing one of the driest months on record, and much of the province is rated at an extreme or high fire risk. There are about 29 active significant wildfires burning across the province.

On Monday, B.C. announced a campfire ban covering all areas of the province except the Kootenay region and the extreme West Coast of Vancouver Island will come into effect on Thursday.