A wind advisory was expected to remain in effect for the Walnut-Diamond Bar region through 4 p.m. Monday, according to the National Weather Service.
Forecasters said the winds were resulting from a "north flow behind a cold low pressure system along the lower Colorado River Valley," which were bringing sustained north winds of 15 miles per hour to 25 mph, with gusts possible up to 45 mph in areas below passes and canyons.
The daytime high Jan. 7 was expected to peak in the low 60s in Diamond Bar and Walnut, and Tuesday was expected to be about 10 degrees warmer, according to the Weather Service.
The overnight low Monday into Tuesday for Diamond Bar and Walnut was expected in the low 40s. A storm system later in the week could bring rain showers and snow at high elevations.