This afternoon’s forecast update is an eye-opener:
BECAUSE FREEZING LEVEL IS EXPECTED TO VERY LOW…EVENTUALLY REACHING
THE SURFACE JUST ABOUT EVERYWHERE TONIGHT…ANY PRECIPITATION MAY BE
IN THE FORM OF SNOW GRAINS/FLURRIES
As promised, a cold storm has blown in. The recent forecasts suggest it will not bring much rain, and it won’t be as cold during the day today* as previously announced, but the nights could turn out to be even colder than expected as of a few days ago. Freeze warnings will be in effect. In fact, the forecast for San Diego valleys now says lows of 22 to 32 Saturday morning and 20 to 30 for early Sunday morning. I can’t recall when I last saw freezing temperatures at the upper end of the forecast range.
Very low (by local standards) temperatures are a mixed blessing for the fruit-grower. Temperatures below 33 are said by experts not to be useful for chill accumulation, but the cool days will still mean that the next several days result in significant net chilling. That is, a day with a low of 38 and high of 64 may actually be better for net chill than a day with a low of 25 and a high of 64, but something on the order of 25-55 should be really good for the deciduous trees. However, those lows could be harmful for the subtropicals, even if it is 7-8 degrees warmer during the coldest part of the night up the slope where most of them are.
* Peaked around 55.