California, 2012

Frost and Freeze and Winter Weather in California, December 17 to 20, 2012

December 17 to 20, 2012 · NWS HNX · 9 events in 5 counties and zones

A warm airmass moved into California on December 17th, ahead of the next storm. Lows in the central and southern San Joaquin Valley were several degrees above normal.

The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
9

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS HNX wrote it up.

A warm airmass moved into California on December 17th, ahead of the next storm. Lows in the central and southern San Joaquin Valley were several degrees above normal. Fresno’s low on the 17th was 52 degrees, tying the record high minimum temperature for the date.

A potent winter storm reached the central California interior on December 18th. This storm brought strong winds to the region, with gusts to 37 mph in the central San Joaquin Valley and gusts to 64 mph in the Kern County deserts and 71 mph in the Kern County mountains. The strong gusts played havoc on traffic traversing Highway 14 at the south end of Tehachapi Pass, with two big rigs blown over during the afternoon of the 18th.

The storm was relative dry, however, and snow accumulations were only 9 inches or less, mainly above the 6500 foot level.

The relatively dry airmass allowed for strong cooling for the central and southern San Joaquin Valley once the winds subsided during the evening of December 18th. Temperatures fell into the mid to upper 20s in the coldest Valley locations, bringing the first significant freeze event to the central and southern San Joaquin Valley. Low temperatures the next morning were even colder by a few degrees, with the coldest spots dropping down to 21 degrees.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Hanford, CA wrote its last area forecast discussion before the first event at Dec 17, 3:10 AM PST, 50 minutes earlier.

Area forecast discussion, Dec 17, 3:10 AM PST, 50 minutes before
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Hazardous weather outlook, Dec 16, 12:53 PM PST, 15 hours 7 minutes before
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Event by event

8 frost/freeze, 1 winter weather. Local standard time, as filed.

Winter Weather, S Sierra Mtns

When
December 17, 4:00 AM PST to December 18, 9:00 AM PST
Where
S Sierra Mtns forecast zone
Reported by
Park/Forest Service

Frost/Freeze, W Central S.J. Valley

When
December 19, 2:00 AM PST to 9:00 AM PST
Where
W Central S.J. Valley forecast zone
Reported by
Mesonet

Frost/Freeze, E Central S.J. Valley

When
December 19, 2:00 AM PST to 9:00 AM PST
Where
E Central S.J. Valley forecast zone
Reported by
Mesonet

Frost/Freeze, Sw S.J. Valley

When
December 19, 2:00 AM PST to 9:00 AM PST
Where
Sw S.J. Valley forecast zone
Reported by
Mesonet

Frost/Freeze, Se S.J. Valley

When
December 19, 2:00 AM PST to 9:00 AM PST
Where
Se S.J. Valley forecast zone
Reported by
Mesonet

Frost/Freeze, W Central S.J. Valley

When
December 20, 12:00 AM PST to 9:00 AM PST
Where
W Central S.J. Valley forecast zone
Reported by
Mesonet

Frost/Freeze, E Central S.J. Valley

When
December 20, 12:00 AM PST to 9:00 AM PST
Where
E Central S.J. Valley forecast zone
Reported by
Mesonet

Frost/Freeze, Sw S.J. Valley

When
December 20, 12:00 AM PST to 9:00 AM PST
Where
Sw S.J. Valley forecast zone
Reported by
Mesonet

Frost/Freeze, Se S.J. Valley

When
December 20, 12:00 AM PST to 9:00 AM PST
Where
Se S.J. Valley forecast zone
Reported by
Mesonet

What these are

Winter Weather
Snow, sleet or freezing rain below warning levels that still caused disruption, damage or casualties.
Frost/Freeze
Frost or temperatures at or below freezing during the growing season, usually filed for crop damage.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in California in 2012Every state in 2012This day in weather historyWarnings in California, December 2012

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-10-01. Each event’s entry at NCEI: 427357, 427358, 427359, 427360, 427361, 427362, 427363, 427364, 427365.