ANNUAL CLIMATOLOGICAL SUMMARY FOR LOS ARCOS MHP, SIERRA VISTA AZ
(1987-2007)
LATITUDE: 31d 32.72m N  LONGITUDE: 110d 17.52m W ELEVATION: 1425.3m
This Summary is based upon observations taken at the
Los Arcos MHP in Sierra Vista during the period of
1987-2007. The official climatological data for Sierra
Vista is derived from data obtained at Fort Huachuca.
The rainfall data uses the newly derived 20 year averages.
TEMPERATURE (All Temperature Data in Degrees F) (1988-2007)
MONTH  Average Maximum   Average Minimum   Average   Extreme Maximum/Year   Extreme Minimum/Year
JAN                59.6                       33.6                   46.6            81/2000                         12/2002
FEB                63.6                       36.1                   49.9            84/1989                         15/2001
MAR               69.5                       39.6                   54.6            92/1989                         18/2002
APR                75.8                       45.7                   60.8            92/1996,00                    23/1999
MAY               84.8                       54.1                   69.1           104/2002,05                   36/1999
JUN                92.0                       62.2                   77.1           106/1990,94                   45/1995,99
JUL                90.6                       65.7                   78.2            107/1995                       51/1998
AUG               87.9                       64.2                   76.1            102/1995                       55/2000
SEP                85.4                       60.3                   72.9             96/1990,95                   44/2004
OCT               77.7                       50.2                   63.9             92/1999                        28/1996
NOV               67.6                       40.1                   53.9             83/1988                        17/2004
DEC               59.6                       32.6                   46.1              76/1995,07                   11/1987
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YEAR             76.2                        48.7                  62.5              107/1995                        11/1987

PRECIPITATION (All Amounts in Inches): (1987-2007)
MONTH   Average Rainfall   Maximum/Year   Minimum/Year   Snowfall    Maximum/Year   Thunderstorms*
JAN              0.91                 4.71/1993              T/2000           1.5             5.6/1997               1.2
FEB              0.83                  2.18/1991          0.03/1999          0.5             5.1/1987               0.9
MAR            0.53                  2.13/1992          0.00/1987,96      0.2             1.5/2006               1.5
APR             0.46                  2.26/1987          0.00/1991,00      0.1             1.0/1999               1.9
MAY            0.29                  1.68/1992          0.00/Many            T               T/1995               4.7
JUN              0.64                 4.81/2000          0.00/1998,02,05    0                   -                     8.5
JUL              3.59                  7.60/2007          1.42/1997             0                   -                   25.6
AUG             4.51                  7.59/1995          1.98/2002             0                  -                    26.4
SEP              1.57                  3.43/2006          0.01/1992             0                  -                    11.1
OCT             1.16                  7.30/2000              T/1999            T                T/1996               4.3
NOV             0.59                  3.75/1994          0.00/1999,05,06 0.1             1.0/2000               1.3
DEC             0.99                  3.77/1994          0.00/2000          1.2             6.0/1987                0.5
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YEAR          16.07                 7.60/2007          0.00/Many         3.6              6.0/1987              87.9
* Observed Thunderstorms-we average 65 days per year with Thunder.
NOTES: In general, minimum temperatures will run cooler here than at FHU due to the presence of a cold air
drainage channel off the mountains. This is especially true in the Winter. The modern extreme low for FHU is
+9F set in 1971 and 1978 for a POR going back to 1954. Historical data shows an extreme low of +1F on
January 7,1913 which is also when Tucson set its all time extreme low of +6F. Extreme lows are much colder
near the San Pedro River where temperatures as low as -6F have been recorded. Willcox at the north end of
the Sulphur Springs Valley has been as cold as -10F. These extreme cold spells are short lived and some years
will go by without any readings below 20F here. Last recorded Frost date is April 30th and the earliest is
October 26th although the normal first and last frosts generally occur in November and March. Because of our
elevation, our highs will run about 8 degrees cooler than Tucson's and the record high for Sierra Vista is 108F
but lower portions of the Valley have exceeded 110F. We average about 5 days per year with 100F but have
never had a year without a 100F reading. During the monsoon we will be much cooler than Tucson but also
quite humid.

Approximately 90% of our Thunderstorms and 65% of our rainfall occurs during the monsoon which runs
from 6 July through 7 September on average. Monsoon thunderstorms can be severe and on average about
1-2 tornadoes (usually small) occur in Cochise County each year. Intense rainfall with the thunderstorms can
cause serious flash flooding. Snow usually occurs as a light dusting at the end of a storm with infrequent
snowstorms. Record for snowfall in Sierra Vista is 18 inches in 1971. Freezing rain has occurred only once.
Fog usually stays down near the river but will come into town on occasion during the Winter. There has been
snow on the ground for Christmas twice-in 1987 and 1997. The Mountains get much more snow of course.

It tends to be breezy here in the Spring with 25-30 mph wind gusts common during March through May
and sometimes even into June. Strong downslope winds can occur close to the mountains during Winter and
Spring storms especially near the Canyons when strong Southwest flow occurs ahead of an approaching storm
system. Fortunately they do not reach far into the Valley as we have recorded gusts as high as 83 mph during
such events here. Thunderstorm winds have reached as high as 92 mph on Post and 89 mph here. On August
23-24,1992, Tropical Storm Lester brought several hours of strong wind gusts which reached 70 mph in the
Valley, 78 mph here and at the base of the Mountains and 85 mph in the Mountains-this has been the most
damaging windstorm during the POR. Large Dust Devils occur in late Spring and early Summer and can cause
significant damage and be accompanied by localized winds in excess of 80 mph. During the strong windstorms
of Spring and sometimes early Summer, the humidity values will fall to very low levels and major wildfires
have occurred during such wind events.