State Precipitation & Temperature Update for Arizona

Conditions through January 2012

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 2/23/2012. The data are preliminary.

Precipitation Percentiles by Watershed (through January 2012)

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Temperature Percentiles by Climate Division (through January 2012)

SHORT TERM CONDITIONS: 1-6 MONTHS

January was extremely dry across western Arizona and slightly drier than normal in eastern Arizona. Eight watersheds were between the 11^th and 20^th percentiles, while seven were between the 20^th and 36^th percentiles. Very few winter storms crossed the state last month, and the few that did dropped scant precipitation on the northern and southern watersheds. Temperatures were much warmer than normal, with many locations recording January among the top ten warmest Januarys in the historical record. Northern Arizona, which saw more storm tracks, was not quite as hot as southern Arizona. The three month precipitation was wetter than average in six watersheds in southern Arizona and near average in eight watersheds in northern Arizona. Virtually all the precipitation fell in November and December. Three month temperatures were near average on the Colorado Plateau and in Yavapai and Yuma counties, and slightly cooler than average in Gila County. Six month precipitation was near average in nine watersheds, slightly drier than average in four, much drier than average in the Lower Colorado, and wetter than average on the Colorado Plateau. Six month temperatures were slightly warmer than normal across Northern Arizona and above the 88^th percentile in southern Arizona.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	47.56	CD1	90.68
Upper Colorado	19.05	CD2	89.83
Little Colorado	26.83	CD3	91.53
Verde	16.67	CD4	85.59
Bill Williams	14.29	CD5	95.76
Agua Fria	19.05	CD6	97.46
Lower Gila	11.90	CD7	95.76
Salt	21.43
Lower Colorado	16.67
Upper Gila	28.57
Santa Cruz	14.29
San Pedro	26.19
Willcox Playa	28.57
San Simon	16.67
White Water Draw	35.37

JANUARY 2012: 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	20.51	CD1	64.10
Upper Colorado	39.02	CD2	44.44
Little Colorado	60.00	CD3	47.86
Verde	55.00	CD4	39.32
Bill Williams	60.98	CD5	57.26
Agua Fria	56.10	CD6	68.80
Lower Gila	70.73	CD7	61.54
Salt	58.54
Lower Colorado	58.54
Upper Gila	65.85
Santa Cruz	60.98
San Pedro	56.41
Willcox Playa	57.50
San Simon	60.98
White Water Draw	62.50

NOVEMBER 2011 - JANUARY 2012 (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	26.32	CD1	70.09
Upper Colorado	31.71	CD2	62.82
Little Colorado	65.00	CD3	82.91
Verde	32.50	CD4	74.36
Bill Williams	31.71	CD5	88.89
Agua Fria	24.39	CD6	93.16
Lower Gila	41.46	CD7	88.89
Salt	29.27
Lower Colorado	17.07
Upper Gila	36.59
Santa Cruz	36.59
San Pedro	41.03
Willcox Playa	47.50
San Simon	26.83
White Water Draw	47.50

AUGUST 2011 – JANUARY 2012 (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 still the driest short-term period, with only the upper Colorado, Little Colorado, and Willcox Playa watersheds near normal. Ten watersheds are below the 20^th percentile and four are below the 10^th percentile. Again, the pattern clearly shows the northern storm tracks across the state in the past year. Temperatures were near average on the Colorado Plateau and in Mohave County, while the southern counties were warmer than average.

The 24-month period cannot be considered a wet long term period, but it may be the least dry. All three long-term periods are quite dry, particularly in southern Arizona. For the 24-month, only four watersheds are near average, with three more slightly drier than average, and eight are below the 20^th percentile, with four of those below the 10^th percentile and two of those below the 5^th percentile. Temperatures for the last 2 years have been near average in the northern counties, and much warmer than average in the southern counties, where conditions have remained very dry.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	20.51	CD1	57.26
Upper Colorado	41.46	CD2	50.43
Little Colorado	46.34	CD3	73.50
Verde	19.51	CD4	82.48
Bill Williams	12.20	CD5	73.08
Agua Fria	7.32	CD6	83.76
Lower Gila	24.39	CD7	88.03
Salt	17.07
Lower Colorado	17.07
Upper Gila	9.76
Santa Cruz	9.76
San Pedro	19.51
Willcox Playa	21.95
San Simon	7.32
White Water Draw	17.50

FEBRUARY 2011 - JANUARY 2012 (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	31.58	CD1	59.91
Upper Colorado	55.00	CD2	55.17
Little Colorado	55.00	CD3	78.02
Verde	22.50	CD4	76.72
Bill Williams	15.00	CD5	75.86
Agua Fria	7.50	CD6	84.48
Lower Gila	32.50	CD7	84.05
Salt	22.50
Lower Colorado	22.50
Upper Gila	10.00
Santa Cruz	2.50
San Pedro	20.00
Willcox Playa	15.00
San Simon	5.00
White Water Draw	15.00

FEBRUARY 2010 - JANUARY 2012 (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 nearly matched by the 48-month period, with both having only four watersheds with no drought. Two are between the 24^th and 29^th percentiles, six are between the10th and 18^th percentiles, one is at the 8^th percentile and two are below the 3^rd percentile. Temperatures for the three year period were slightly warmer than average in northern Arizona, and much warmer in the southern counties, above the 90^th percentile.

The 48-month period has a similar pattern, but the Virgin watershed is below 12^th percentile rather than at the 24^th, and the Bill Williams is at the 8^th rather than the 13^th percentile, and San Simon is better, at the 5^th rather than the 3^rd percentile. The 48 month period remains the warmest long term period, with Maricopa and Pinal counties above the 96^th percentile. All the northern counties are below the 75^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	24.32	CD1	63.91
Upper Colorado	51.28	CD2	61.30
Little Colorado	48.72	CD3	77.39
Verde	12.82	CD4	76.09
Bill Williams	12.82	CD5	81.74
Agua Fria	7.69	CD6	90.43
Lower Gila	38.46	CD7	90.43
Salt	30.77
Lower Colorado	28.21
Upper Gila	17.95
Santa Cruz	2.56
San Pedro	17.95
Willcox Playa	17.95
San Simon	2.56
White Water Draw	12.82

FEBRUARY 2009 - JANUARY 2012 (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	66.96
Upper Colorado	52.63	CD2	74.56
Little Colorado	31.58	CD3	78.07
Verde	10.53	CD4	67.11
Bill Williams	7.89	CD5	82.46
Agua Fria	5.26	CD6	96.49
Lower Gila	55.26	CD7	85.53
Salt	47.37
Lower Colorado	26.32
Upper Gila	18.42
Santa Cruz	2.63
San Pedro	13.16
Willcox Playa	15.79
San Simon	5.26
White Water Draw	15.79

FEBRUARY 2008- JANUARY 2012 (48-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

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

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

SUMMARY

January was extremely dry across western Arizona and slightly drier than normal in eastern Arizona. Eight watersheds were between the 11^th and 20^th percentiles, while seven were between the 20^th and 36^th percentiles. Very few winter storms crossed the state last month, and the few that did dropped scant precipitation on the northern and southern watersheds. Temperatures were much warmer than normal, with many locations recording January among the top ten warmest Januarys in the historical record. Northern Arizona, which saw more storm tracks, was not quite as hot as southern Arizona.

The 3-month precipitation was wetter than average in six watersheds in southern Arizona and near average in eight watersheds in northern Arizona. Virtually all the precipitation fell in November and December. Three month temperatures were near average on the Colorado Plateau and in Yavapai and Yuma counties, and slightly cooler than average in Gila County.

The 6-month precipitation was near average in nine watersheds, slightly drier than average in four, much drier than average in the Lower Colorado, and wetter than average on the Colorado Plateau. Six month temperatures were slightly warmer than normal across Northern Arizona and above the 88^th percentile in southern Arizona.

The 12-month period is still the driest short-term period, with only the upper Colorado, Little Colorado, and Willcox Playa watersheds near normal. Ten watersheds are below the 20^th percentile and four are below the 10^th percentile. Again, the pattern clearly shows the northern storm tracks across the state in the past year. Temperatures were near average on the Colorado Plateau and in Mohave County, while the southern counties were warmer than average.

The 24-month period cannot be considered a wet long term period, but it may be the least dry. All three long-term periods are quite dry, particularly in southern Arizona. For the 24-month, only four watersheds are near average, with three more slightly drier than average, and eight are below the 20^th percentile, with four of those below the 10^th percentile and two of those below the 5^th percentile. Temperatures for the last 2 years have been near average in the northern counties, and much warmer than average in the southern counties, where conditions have remained very dry.

The 36-month period is nearly matched by the 48-month period, with both having only four watersheds with no drought. Two are between the 24^th and 29^th percentiles, six are between the10th and 18^th percentiles, one is at the 8^th percentile and two are below the 3^rd percentile. Temperatures for the three year period were slightly warmer than average in northern Arizona, and much warmer in the southern counties, above the 90^th percentile.

The 48-month period has a similar pattern, but the Virgin watershed is below 12^th percentile rather than at the 24^th, and the Bill Williams is at the 8^th rather than the 13^th percentile, and San Simon is better, at the 5^th rather than the 3^rd percentile. The 48 month period remains the warmest long term period, with Maricopa and Pinal counties above the 96^th percentile. All the northern counties are below the 75^th percentile.