Hours after a red flag warning expired, signaling the end of critical fire weather conditions for now, a frost advisory was in effect Friday morning in most of Riverside County, including the Riverside metropolitan area and the Coachella Valley.
The National Weather Service frost advisory, which went into effect at 10 p.m. Thursday and was set to expire at 9 a.m. today, means that widespread frost is expected, sensitive outdoor plants may be killed if left uncovered, and appropriate arrangements must be made to protect outdoor pets.
Areas under the frost advisory included Riverside, Moreno Valley, Indio, Cathedral City, Palm Desert, Palm Desert Country, Coachella, Banning and Desert Hot Springs.
One resident from Temple City reported that temps in the area were nearly 35 degrees.
NWS forecasters predicted overnight low temperatures of 32 to 35 degrees across most of the county, with isolated temperatures as low as 27 to 32 degrees.
As of 3:30 a.m., it was 28 degrees at the March Air Reserve Base, 42 degrees in Riverside and 47 degrees in Coachella and Indio.
The frost advisory went into effect four hours after the expiration of a red flag warning, which was issued due to strong Santa Ana winds and low humidity levels. During that warning, a brushfire broke out in the Santa Ana River bottom near downtown Riverside, blackening 50 acres and spawning multiple spot fires amid high winds.
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As of 4 p.m. Thursday, the forward spread of the so-called "Riverbottom Fire" was stopped and the blaze was 50 percent contained.
