Drive BC says the best alternate route was by Highway 3 and Highway 5A to Merritt and then Highway 5.
Its website is also experiencing technical difficulties so some events are not updating correctly, according to the Drive BC Twitter account.
The wildfire forcing the closure is the July Mountain blaze, estimated at 7,476 hectares.
The fire was out of control, and there has been growth on the south end and the northeast flank, adjacent to the highway, in the past 24 hours.
The July Mountain wildfire has already forced the evaluation order for 98 properties in Electoral Area “N.”
Anyone travelling in this area is being asked to check Drive BC before heading out as situations may change at any time.
The B.C. government said Sunday that as fire conditions can change quickly, drivers should be aware that provincial highways may close with limited notice.
Non-essential travel to and within fire-affected areas is discouraged to help avoid traffic congestion on evacuation routes.
If anyone must travel on Interior highways adjacent to wildfires, they are asked to be prepared for possible delays or closures. Travel with a full tank of gas, food, water and other emergency supplies.