A rainfall warning has been issued for the Bulkley Valley and The Lakes.
Environment Canada says a low pressure system will bring in heavy periods of rain over the next 24 hours.
Totals of 40-50 millimetres is expected for Smithers, Telkwa and Houston through tomorrow evening.
A severe thunderstorm watch is also in place for the southern portions of the Bulkley Valley, including Burns Lake.
Officials from the River Forecast Centre have issued a high streamflow advisory for the Bulkley River, warning of rapid increase in levels as the storm moves through.
The rain totals are expected to decrease by Saturday and officials are urging everyone to stay away from creeks and rivers.
The northwest is not the only area expected to get hit by large amounts of rain.
A rainfall warning is in effect for the north and south Peace River regions where they could see up to 70 millimetres of rain by late Friday.
Also, the Cariboo is under a severe thunderstorm watch.