The B.C. River Forecast Centre has issued a flood watch for the river at Prince George and north, and a high water advisory for south of Prince George through the Fraser Canyon to the coast.
Recent heat and rain have combined to cause a rapid snowmelt that has swollen the river.
The forecast centre says levels on the Upper Fraser River are expected to continue to rise sharply through Tuesday and Wednesday if rain is heavy in the region, while peak levels may be reached on the lower Fraser River on Friday or Saturday.
Meanwhile, the centre is maintaining a flood watch for the Birkenhead River near Pemberton and high streamflow advisory for those near the Squamish and Lillooet rivers and tributary creeks through the Sea-to-Sky corridor and Pemberton Valley.
However, it says levels on Squamish, Lillooet and Cheakamus rivers have all been dropping and may fall more with the arrival of cooler weather.