RIVERSIDE – A cooling trend will begin in Riverside County Friday, forecasters said.

The National Weather Service said upper low pressure will move through southwest California Saturday into Sunday.

Temperatures Friday in the valleys were expected to peak in the low 80s, compared to the mid-90s Thursday. In the mountains, highs were expected to be in the mid-70s, compared to mid-80s Thursday, forecasters said.

There is a possibility of rain in all areas of the county on Saturday, according to NWS forecasters, who, as of Friday morning, projected a 30 percent chance of rain in the valleys and a 20 to 40 percent chance of rain in mountain areas.

If the rain materializes, it may be accompanied by strong, gusty winds of up to 25 miles per hour in the valleys and 45 mph in the mountains through Sunday, forecasters said.

Daytime temperatures through the county will average about 10 degrees below normal Sunday, according to the weather service.