The Met Office has warned motorists to expect "difficult driving conditions" but said the heaviest and most persistent rain is expected to fall on high ground.
The warning has been issued from 12:00 GMT on Saturday to 23:55 on Sunday.
It follows a warning of icy conditions on Friday morning.
The conditions led to a number of accidents on the roads, including on the A467 in Newbridge, Caerphilly county.
The weekend rain warning covers Conwy, Denbighshire, Flintshire, Gwynedd, Powys, Wrexham and Ceredigion.
Forecasters have issued a yellow "be aware" warning for rain over the weekend.