Some 80 firefighters are prepared for high temperatures and changing winds as they continue to battle a 600-hectare wildfire today in B.C.'s Yalakom Valley.

Upwards of 85 residents in 20 homes remain on evacuation alert in the area, 30 kilometres northwest of Lillooet.

Crews today have been constructing a machine guard on the northeast flank of the fire and completing a contingency line on the southwest side.

Officials describe the blaze that began Wednesday as moderate and mostly on the ground, but said fire activity could still increase due to conditions.

Seven helicopters, 14 structure protection unit personnel and five pieces of heavy equipment joined firefighters Saturday.

Leslie Lloyd with the Squamish Lillooet Regional District says officials are closely monitoring the behaviour and threat level of the fire to determine whether the alert is sufficient.