Byron, CA

... January 2012 regional climate summary...

Summary for the San Francisco Bay area and Monterey Bay area...

Except for a five day period of wet weather from January 19 to
January 23... the weather across the San Francisco Bay area and
Monterey Bay area during January 2012 was very much like that of
December 2011. Most January days were sunny... dry and warm... and
most nights were clear and cool.

2012 got off to a warm start. Three daily high temperature records
were set on January 1st. A brief cool-down on the 2nd and 3rd was
followed by an extended warm and dry period from the 4th through
the 14th. Daytime temperatures were above normal on ten of these
eleven days and several daily high temperature records were set or
tied on the 4th... 5th and 7th. The upper ridge that produced
record warmth during the first several days of January... and dry
weather for the first half of the month... weakened by the middle
of the month. This allowed a cold upper trough along the British
Columbia coast to drop south into California on the 15th and 16th.
This upper trough was dry... but the airmass it ushered into our
area was sufficiently cold to produce widespread freezing
temperatures across our region from the 16th through the 18th.
Record low temperature records were set or tied on the mornings of
the 17th and 18th. The coldest temperatures of the month for most
of the area occurred early on the morning of Tuesday the 17th. The
low temperature at the Napa Airport that morning was 19... while
most other inland valley locations recorded low temperatures in
the lower to mid 20s. Upper 20s and lower 30s were common
elsewhere during the early morning hours of the 17th.

When the upper ridge weakened around the middle of the month... moist
flow across the Pacific was finally able to break through to the
West Coast. Rain began to fall on the 19th and then became locally
heavy on Friday the 20th... continuing into Friday night. Rain
totals from Thursday January 19 through Saturday January 21
ranged from 2.5 to 5.75 inches in the North Bay... and from 1 to 3
inches across most of the rest of the region except as little as
0.25 inches in the interior valleys and as much as 7 inches in the
Santa Cruz and Santa Lucia mountains. A second system dropped
more rain from late Sunday into Monday the 23rd. The second system
produced strong and gusty southerly winds on Sunday night and
early Monday when widespread wind gusts of between 40 and 50 mph
were recorded... along with local gusts up to 60 mph. Rain totals
with the second system were not quite as impressive as with the
first but still significant... especially in the coastal mountain
ranges where as much as four more inches of rain fell on the 22nd
and 23rd.

All of january's rainfall occurred during the 5 day period from
the 19th to the 23rd. The North Bay benefited most from this brief
respite from the prolonged dry period. January rainfall totals at
North Bay climate stations were close to normal... or even slightly
above normal. Elsewhere... rain totals for January ranged anywhere
from about 40% to 70% of normal. Year-t0-date rainfall totals
jumped significantly by the 23rd... but still lagged well behind
normal. Below is a listing of year-to-date rain totals prior to
January 19 and then again on January 23.

                      Year-to-date year-to-date
                      totals on totals on
                      January 18: January 23:
location inches/pon inches/pon

Santa Rosa Airport 4.46/23% 11.43/58%
San Francisco 3.37/29% 6.05/49%
sfo Airport 2.87/28% 5.03/47%
Oakland Airport 3.07/29% 5.24/48%
Moffett field 1.77/26% 2.80/39%
San Jose Airport 1.55/22% 2.45/33%
Salinas Airport 3.31/59% 4.91/82%

Temperatures during the wet period from the 19th to the 23rd were
opposite of what they were during most of the rest of January.
Daytime highs were cool... mostly in the 50s... while nights were
relatively mild due to considerable cloud cover.

The typical dry weather pattern of the current winter season
returned by January 25. For the remainder of the month our
region experienced dry and mild weather conditions as a ridge of
high pressure once again persisted along the West Coast.

Average high temperatures for the month were above normal at all
climate stations... generally from 2 to 5 degrees warmer than
normal. Low temperatures were below normal at most climate station
locations. The exceptions were a few locations near the immediate
coast and at higher elevation where average lows were above normal.


           ... January regional temperature summary...

                                departure departure
                   avg normal from avg normal from
location high high normal low low normal

North Bay...

Calistoga 62.7 59.5 3.2 30.5 37.3 -6.8
Healdsburg 60.1 57.6 2.5 36.0 39.6 -3.6
Kentfield 59.5 55.0 4.5 40.5 41.3 -0.8
Napa 61.8 57.3 4.5 36.9 39.4 -2.5
Napa Airport 61.1 55.1 6.0 32.7 37.0 -4.3
Petaluma Airport 60.9 56.9 4.0 35.2 39.2 -4.0
Saint Helena 62.8 57.8 5.0 37.6 38.6 -1.0
Santa Rosa 63.3 59.0 4.3 35.2 39.2 -4.0
Santa Rosa ap 61.9 56.7 5.2 33.5 36.6 -3.1
Sonoma 60.2 56.3 3.9 35.7 37.8 -2.1

San Francisco peninsula...

Half Moon Bay 61.0 59.0 2.0 41.1 41.5 -0.4
Redwood City 61.4 58.0 3.4 37.9 40.4 -2.5
San Francisco
Airport 58.1 56.3 1.8 43.0 44.2 -1.2
San Francisco
downtown 59.3 56.9 2.4 46.5 45.7 0.8
Woodside 64.6 60.5 4.1 32.8 37.0 -4.2

East Bay...

Berkeley 61.6 58.4 3.2 43.0 42.0 1.0
Concord Airport 60.9 55.9 5.0 37.0 39.7 -2.7
Fremont 60.7 58.1 2.6 39.9 42.2 -2.3
Hayward Airport 59.2 57.2 2.0 41.0 42.5 -1.5
Livermore ap 61.7 56.0 5.7 36.4 37.4 -1.0
Martinez 59.8 55.2 4.6 32.7 35.6 -2.9
Mount Diablo
Junction 57.6 55.5 2.1 42.8 40.0 2.8
Newark 59.9 57.6 2.3 41.2 42.1 -0.9
Oakland 62.2 58.1 4.1 43.9 44.3 -0.4
Oakland Airport 57.7 56.9 0.8 38.3 41.7 -3.4

South Bay and Santa Cruz County...

Ben Lomond 68.6 61.5 7.1 33.4 37.0 -3.6
Gilroy 64.9 60.4 4.5 37.5 38.0 -0.5
Moffett field 62.0 58.7 3.3 41.7 42.9 -1.2
Mount Hamilton 53.5 48.7 4.8 41.5 38.4 3.1
San Jose 61.8 58.1 3.7 39.9 42.0 -2.1
Watsonville 65.0 60.9 4.1 37.5 39.4 -1.9
Watsonville ap 65.5 61.3 4.2 40.1 39.5 0.6

Monterey and San Benito counties...

Carmel Valley 66.4 61.9 4.5 38.1 39.2 -1.1
Hollister 62.5 60.1 2.4 36.6 38.2 -1.6
King City 66.6 63.6 3.0 34.6 37.7 -3.1
Monterey 61.2 58.3 2.9 44.2 43.7 0.5
Monterey Airport 61.8 59.5 2.3 41.4 42.5 -1.1
Salinas 66.5 62.3 4.2 38.2 39.5 -1.3
Salinas Airport 65.1 61.3 3.8 39.9 41.3 -1.4


        ... January regional precipitation summary...

                             normal
                   Jan Jan percent
location total precip of normal

North Bay...

Calistoga 6.92 8.16 85
Cloverdale 6.30 8.43 75
Fort Ross 7.38 7.23 102
Healdsburg 9.41 8.54 110
Kentfield 8.28 9.13 91
Muir Woods 5.37 6.97 77
Napa 4.89 5.13 95
Napa Airport 4.00 4.38 91
occidental 11.82 11.11 106
Petaluma Airport 4.61 4.93 94
Saint Helena 5.77 6.94 83
Santa Rosa 6.31 5.93 106
Sonoma County ap 6.97 7.05 99
Sonoma 4.92 6.02 82

San Francisco peninsula...

Half Moon Bay 2.18 5.53 39
Palo Alto 1.84 3.06 60
Redwood City 2.82 4.02 70
San Francisco
Airport 2.16 4.19 52
San Francisco
downtown 2.68 4.50 60
Woodside 4.10 5.98 69

East Bay...

Berkeley 3.38 4.98 68
Concord Airport 2.38 3.27 73
Fremont 1.19 3.07 39
Hayward Airport 1.56 3.30 47
Livermore 1.52 2.87 53
Livermore Airport 1.64 3.01 54
Martinez 2.87 4.01 72
Mount Diablo
Junction 3.81 4.77 80
Newark 0.95 2.95 32
Oakland 2.83 4.71 60
Oakland Airport 2.17 3.99 54

South Bay and Santa Cruz County...

Ben Lomond 8.81 10.06 88
Gilroy 4.40 4.38 100
Los Gatos 1.99 4.94 40
Moffett field 1.03 2.75 37
Mount Hamilton 3.15 4.68 67
San Jose 0.90 3.07 29
Santa Cruz 3.68 6.28 59
Watsonville 2.81 4.46 63
Watsonville ap 2.69 3.81 71

Monterey and San Benito counties...

Carmel Valley 2.32 3.82 61
Hollister 1.65 2.93 56
King City 1.30 2.32 56
Monterey 1.86 4.40 42
Monterey Airport 1.31 3.17 41
Pinnacles Nat Mon 1.52 3.48 44
Salinas 1.41 3.09 46
Salinas Airport 1.60 2.60 62


    ... daily temperature records for January 2012...


                                  record
                                  maximum previous
                                  temp record

1/01 Oakland museum 67 66 in 1997

1/01 Moffett field 70 69 in 1994

1/01 Gilroy 72 69 in 1980

1/04 Moffett field 69 66 in 1986

1/04 Santa Rosa 72 72 in 1919

1/04 Livermore 69 69 in 1914

1/05 Oakland museum 67 66 in 2001

1/05 Moffett field 67 67 in 1986

1/05 Santa Rosa 70 70 in 2003

1/07 Kentfield 68 66 in 1943

1/07 Santa Rosa 70 70 in 1911

1/07 Richmond 67 67 in 2003


                                  record
                                  minimum previous
                                  temp record

1/17 Oakland museum 34 36 in 1997

1/17 Oakland Airport 28 32 in 2001

1/17 San Jose 29 30 in 1943

1/17 Napa 23 24 in 1963

1/17 Richmond 33 33 in 1963

1/17 Moffett field 29 29 in 1947

1/17 Santa Cruz 26 26 in 1917

1/17 Salinas Airport 27 27 in 1987

1/18 Oakland Airport 30 31 in 2007



      ... monthly ranks for downtown San Francisco...

Average high temperature... .59.3... .11th warmest out of 136 years
average low temperature... ..46.5... .42nd warmest out of 136 years
precipitation... ... ... .. 2.68 in... .53rd driest out of 162 years


      ... monthly extremes for select locations...

                     warmest coolest wettest
location day(s) day(s) day(s)


Santa Rosa Airport 1/05 1/07 1/27 1/17 1/20
                     70 deg 21 deg 2.77 in

San Francisco 1/04 1/07 1/17 1/20
                     66 deg 40 deg 1.41 in

San Jose 1/01 1/07 1/08
                     1/13 1/17 1/20
                     68 deg 29 deg 0.44 in

Salinas Airport 1/13 1/17 1/20
                     77 deg 27 deg 0.60 in



Note: this climatological data is preliminary. For official
certified climatological data please contact the National
climatic data center at 828-271-4800 or http://www.Ncdc.NOAA.Gov.
Official values as determined at the above web site may take
several months for authentication and publication.