Saskatchewan travellers are being advised to check ahead before heading out, as heavy fog in some areas is making conditions treacherous.

Early Friday evening the province's Highway Hotline noted there was zero visibility on Highway 39 between Moose Jaw and Weyburn. Parts of Highway 6, south of Regina, were also shrouded in fog.

To make matters worse, the weather forecast calls for freezing rain on roads that were already described as having icy patches.

Road conditions may have been a factor in a serious crash north of Saskatoon's airport early Friday evening, RCMP said.

The crash, on a rural road, happened when a mini-van crossed over into the opposite lane of traffic and collided with an SUV. Emergency crews needed special tools to pry open one of the vehicles to extract the injured occupants. Both people in one of the vehicles were taken to hospital. One person was in critical condition.

skpic highway camera foggy

One of the province's Highway Cams shows reduced visibility. This is a view of Highway 11, around Davidson shortly after 8 p.m. Friday. (Highway Hotline)

The people in the second vehicle were OK after the crash.

RCMP were advising people to be very careful.

Air travellers are also reporting that flights into Regina were being affected by fog, although that was not officially confirmed.