State Precipitation & Temperature Update for Arizona

Conditions through December 2011

Precipitation is monitored for the state of Arizona across the 15 major watersheds (see map left). From the stations within each watershed, mean values of precipitation for the watershed as a whole are computed. These mean values are ranked against the monthly mean values for the period of 1971-present. The rankings are then divided by the number of years of data and multiplied by 100% to create percentiles.

Here, precipitation percentile values for the most recent month, along with previous 3-, 6-, 12-, 24-, 36-, and 48-month total are shown for each watershed. Low percentile values (brown shading) indicate dry conditions while high values (green shading) indicate wet conditions. For example, a precipitation total that falls at the 100^th percentile means that it is the highest precipitation total for the 1971-present period.

Temperature is monitored for the state of Arizona across seven climate divisions (see map left). From the stations within each climate division, mean values of temperature for the climate division as a whole are computed. These mean values are ranked against the monthly mean values for the period of 1895-present. The rankings are then divided by the number of years of data and multiplied by 100% to create percentiles.

Here, temperature percentile values for the most recent month, along with previous 3-, 6-, 12-, 24-, 36-, and 48-month averages are shown for each climate division. Low percentile values (blue shading) indicate cool conditions while high values (orange/red shading) indicate hot conditions. For example, a temperature that falls at the 100^th percentile means that it is the highest average temperature for the 1895-present period.

The maps of the seven periods for precipitation and temperature are shown below, with tables of the percentile values and descriptive text following the maps. The percentiles have shifted to reflect the percentile categories used in the National Drought Monitor. Current update is 1/25/2012. The data are preliminary.

Precipitation Percentiles by Watershed (through December 2011)

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Temperature Percentiles by Climate Division (through December 2011)

SHORT TERM CONDITIONS: 1-6 MONTHS

December was much wetter than average in 14 watersheds, and near average in the Virgin. The wettest watersheds were the Bill Williams, Salt, Agua Fria and Little Colorado. December was even wetter than November. A series of cold winter storms moved through in the first 3 weeks of the month. Temperatures were much colder than normal as a result of the storms. The three month precipitation was wetter than average in eight watersheds and near average in seven. Three month temperatures were colder than normal on the Colorado Plateau and in Yavapai and Gila counties. Six month precipitation was near or drier than average in all watersheds except the Little Colorado, with the Bill Williams, Agua Fria, Virgin, Santa Cruz and San Simon watersheds all between the 25^th and 40^th percentiles. Six month temperatures were near or slightly warmer than normal across Northern Arizona and above the 75^th percentile in southern Arizona.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	51.22	CD1	43.16
Upper Colorado	65.85	CD2	20.09
Little Colorado	82.93	CD3	20.51
Verde	67.50	CD4	17.95
Bill Williams	90.24	CD5	20.94
Agua Fria	75.61	CD6	25.21
Lower Gila	68.29	CD7	22.22
Salt	75.61
Lower Colorado	73.17
Upper Gila	73.17
Santa Cruz	73.17
San Pedro	71.79
Willcox Playa	70.73
San Simon	70.73
White Water Draw	73.17

DECEMBER 2011: percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	42.50	CD1	56.47
Upper Colorado	56.10	CD2	30.34
Little Colorado	73.17	CD3	32.05
Verde	70.00	CD4	34.19
Bill Williams	80.49	CD5	50.43
Agua Fria	68.29	CD6	64.10
Lower Gila	70.73	CD7	50.85
Salt	56.10
Lower Colorado	70.73
Upper Gila	56.10
Santa Cruz	58.54
San Pedro	56.41
Willcox Playa	55.00
San Simon	68.29
White Water Draw	60.98

OCTOBER 2011 - DECEMBER 2011 (3-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	38.46	CD1	71.55
Upper Colorado	56.10	CD2	55.13
Little Colorado	73.17	CD3	75.21
Verde	52.50	CD4	79.49
Bill Williams	39.02	CD5	86.32
Agua Fria	36.59	CD6	90.60
Lower Gila	56.10	CD7	82.91
Salt	58.54
Lower Colorado	41.46
Upper Gila	41.46
Santa Cruz	34.15
San Pedro	53.85
Willcox Playa	47.50
San Simon	26.83
White Water Draw	42.50

JULY 2011 – DECEMBER 2011 (6-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

INTERMEDIATE TERM CONDITIONS: 12-24 MONTHS

The 12-month period is by far the driest short-term period, with the upper Colorado and Little Colorado watersheds near normal. Thirteen watersheds are below the 25^th percentile and eight are below the 15^th percentile. Temperatures were slightly cooler than average on the Colorado Plateau, and slightly warmer than average in Yuma, La Paz, and Yavapai counties. Mohave County was near average, and the southeastern and southern counties were much warmer than average.

The 24-month period continues as the wettest long-term interval with five watersheds above the 62^nd percentile. Four watersheds are near average, four are slightly drier than average and two are below the 18^th percentile. Temperatures for the last 2 years have been much warmer than average in the southern half of the state and only slightly warmer than average in the northern counties.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	15.38	CD1	56.03
Upper Colorado	46.34	CD2	36.21
Little Colorado	39.02	CD3	68.97
Verde	14.63	CD4	81.90
Bill Williams	19.51	CD5	67.24
Agua Fria	12.20	CD6	80.60
Lower Gila	24.39	CD7	84.05
Salt	12.20
Lower Colorado	19.51
Upper Gila	12.20
Santa Cruz	7.32
San Pedro	17.07
Willcox Playa	14.63
San Simon	7.32
White Water Draw	14.63

JANUARY 2011 - DECEMBER 2011 (12-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	39.47	CD1	62.17
Upper Colorado	82.50	CD2	51.74
Little Colorado	70.00	CD3	77.39
Verde	47.50	CD4	76.09
Bill Williams	42.50	CD5	76.52
Agua Fria	35.00	CD6	85.22
Lower Gila	70.00	CD7	80.00
Salt	65.00
Lower Colorado	62.50
Upper Gila	50.00
Santa Cruz	17.50
San Pedro	50.00
Willcox Playa	27.50
San Simon	15.00
White Water Draw	27.50

JANUARY 2010 - DECEMBER 2011 (24-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

LONG TERM CONDITIONS: 36-48 MONTHS

The 36-month period is still the driest long-term interval, with the upper Colorado watershed much wetter than normal and five others near or only slightly drier than normal. Nine watersheds are below the 18^th percentile and three of those are below the 8^th percentile. Temperatures for the three year period were much warmer than average everywhere, with the southern counties above the 90^th percentile.

The 48-month period has the upper Colorado and lower Gila much wetter than average and most of the other watersheds much drier than average. Nine are below the 24^th percentile and four of those are below the 14^th percentile. The 48 month period remains the warmest long term period, but only Maricopa and Pinal counties are above the 95^th percentile. All the northern counties are below the 70^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	27.03	CD1	67.54
Upper Colorado	61.54	CD2	64.04
Little Colorado	43.59	CD3	77.19
Verde	17.95	CD4	77.19
Bill Williams	15.38	CD5	80.70
Agua Fria	7.69	CD6	93.86
Lower Gila	46.15	CD7	90.35
Salt	35.90
Lower Colorado	35.90
Upper Gila	15.38
Santa Cruz	2.56
San Pedro	17.95
Willcox Playa	17.95
San Simon	2.56
White Water Draw	12.82

JANUARY 2009 - DECEMBER 2011 (36-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	11.43	CD1	65.49
Upper Colorado	73.68	CD2	69.03
Little Colorado	42.11	CD3	77.88
Verde	21.05	CD4	61.95
Bill Williams	15.79	CD5	82.74
Agua Fria	13.16	CD6	95.58
Lower Gila	60.53	CD7	85.84
Salt	52.63
Lower Colorado	36.84
Upper Gila	23.68
Santa Cruz	5.26
San Pedro	26.32
Willcox Playa	18.42
San Simon	7.89
White Water Draw	15.79

JANUARY 2008- DECEMBER 2011 (48-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

January 2012 Arizona Drought Update (based on precipitation data through December 2011)

The following summary describes the heat and dryness across the state for the 1-, 3-, 6-, 12-, 24-, 36-, and 48-month periods.

SUMMARY

December was much wetter than average in 14 watersheds, and near average in the Virgin. The wettest watersheds were the Bill Williams, Salt, Agua Fria and Little Colorado. December was even wetter than November. A series of cold winter storms moved through in the first 3 weeks of the month. Temperatures were much colder than normal as a result of the storms. The three month precipitation was wetter than average in eight watersheds and near average in seven.

The 3-month period was wetter than average in eight watersheds and near average in seven. Three month temperatures were colder than normal on the Colorado Plateau and in Yavapai and Gila counties.

The 6-month period was near or drier than average in all watersheds except the Little Colorado, with the Bill Williams, Agua Fria, Virgin, Santa Cruz and San Simon watersheds all between the 25^th and 40^th percentiles. Six month temperatures were near or slightly warmer than normal across Northern Arizona and above the 75^th percentile in southern Arizona.

The 12-month period is by far the driest short-term period, with the upper Colorado and Little Colorado watersheds near normal. Thirteen watersheds are below the 25^th percentile and eight are below the 15^th percentile. Temperatures were slightly cooler than average on the Colorado Plateau, and slightly warmer than average in Yuma, La Paz, and Yavapai counties. Mohave County was near average, and the southeastern and southern counties were much warmer than average.

The 24-month period continues as the wettest long-term interval with five watersheds above the 62^nd percentile. Four watersheds are near average, four are slightly drier than average and two are below the 18^th percentile. Temperatures for the last 2 years have been much warmer than average in the southern half of the state and only slightly warmer than average in the northern counties.

The 36-month period is still the driest long-term interval, with the upper Colorado watershed much wetter than normal and five others near or only slightly drier than normal. Nine watersheds are below the 18^th percentile and three of those are below the 8^th percentile. Temperatures for the three year period were much warmer than average everywhere, with the southern counties above the 90^th percentile.

The 48-month period has the upper Colorado and lower Gila much wetter than average and most of the other watersheds much drier than average. Nine are below the 24^th percentile and four of those are below the 14^th percentile. The 48 month period remains the warmest long term period, but only Maricopa and Pinal counties are above the 95^th percentile. All the northern counties are below the 70^th percentile.