State Precipitation & Temperature Update for Arizona

Conditions through April 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 6/25/2012. The data are preliminary.

Precipitation Percentiles by Watershed (through April 2012)

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Temperature Percentiles by Climate Division (through April 2012)

SHORT TERM CONDITIONS: 1-6 MONTHS

April had near average precipitation in 12 watersheds, slightly more precipitation than average in the Lower Colorado, and below average precipitation in the Virgin and White Water Draw watersheds. Two storm systems moved through Arizona, one in the middle of the month, and the other near the end of April. Most of the rainfall was down in Yuma County or across northern Arizona. The first system dropped some late snow on the higher elevations in northern Arizona. Other than the one cold storm in mid April, temperatures were well above average for all counties except Gila County, which was near average. The three month period is still the driest short-term interval with all but three watersheds below the 29^th percentile, and five below the 17^th percentile. Three month temperatures were much warmer than average, above the 75^th percentile, in all counties except Gila. Six month precipitation was near average in all watersheds except the Verde and the Virgin watersheds, at the 30^th and 8^th percentile, respectively. Six month temperatures were slightly warmer than normal across the state.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	7.14	CD1	88.14
Upper Colorado	40.48	CD2	90.68
Little Colorado	35.71	CD3	88.98
Verde	52.38	CD4	44.07
Bill Williams	59.52	CD5	87.29
Agua Fria	50.00	CD6	89.83
Lower Gila	38.10	CD7	92.37
Salt	45.24
Lower Colorado	73.81
Upper Gila	33.33
Santa Cruz	35.71
San Pedro	32.14
Willcox Playa	35.71
San Simon	33.33
White Water Draw	21.43

April 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	11.90	CD1	82.91
Upper Colorado	23.81	CD2	81.78
Little Colorado	23.81	CD3	75.85
Verde	28.57	CD4	56.78
Bill Williams	35.71	CD5	75.85
Agua Fria	33.33	CD6	86.44
Lower Gila	14.29	CD7	84.32
Salt	11.90
Lower Colorado	26.19
Upper Gila	21.43
Santa Cruz	14.29
San Pedro	16.67
Willcox Playa	26.83
San Simon	30.95
White Water Draw	23.81

February 2012 - April 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	7.69	CD1	73.73
Upper Colorado	31.71	CD2	72.88
Little Colorado	37.50	CD3	68.64
Verde	30.00	CD4	52.54
Bill Williams	48.78	CD5	61.02
Agua Fria	39.02	CD6	79.66
Lower Gila	39.02	CD7	75.85
Salt	36.59
Lower Colorado	31.71
Upper Gila	41.46
Santa Cruz	36.59
San Pedro	30.77
Willcox Playa	45.00
San Simon	51.22
White Water Draw	50.00

November 2011 – April 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 was drier than average in 12 of the 15 watersheds, with the White Water Draw, upper and Little Colorado receiving near average precipitation. Temperatures were much warmer than average, above the 80^th percentile, in the southern two thirds of the state.

The 24-month period is still the driest long-term interval with all but two watersheds, the upper and Little Colorado, below the 18^th percentile. This is largely due to two consecutive La Niña winters where the few storms that crossed through Arizona passed over the upper Colorado and little Colorado watersheds. Temperatures for the last 2 years have been much warmer than average everywhere in the state, but warmest in the southern two thirds of Arizona.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	19.23	CD1	62.39
Upper Colorado	31.71	CD2	70.51
Little Colorado	48.78	CD3	82.91
Verde	14.63	CD4	81.20
Bill Williams	14.63	CD5	80.34
Agua Fria	19.51	CD6	87.18
Lower Gila	24.39	CD7	88.89
Salt	17.07
Lower Colorado	17.07
Upper Gila	24.39
Santa Cruz	14.63
San Pedro	29.27
Willcox Playa	27.50
San Simon	12.20
White Water Draw	32.50

May 2011 - April 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	15.79	CD1	65.52
Upper Colorado	37.50	CD2	75.00
Little Colorado	50.00	CD3	81.03
Verde	17.50	CD4	83.19
Bill Williams	10.00	CD5	81.03
Agua Fria	5.00	CD6	91.38
Lower Gila	12.50	CD7	93.97
Salt	17.50
Lower Colorado	15.00
Upper Gila	5.00
Santa Cruz	2.50
San Pedro	7.50
Willcox Playa	12.50
San Simon	2.50
White Water Draw	15.00

May 2010 - April 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 has four watersheds with near average precipitation and three watersheds slightly drier than average. Eight watersheds are below the 16^th percentile and two of those are below the 3^rd percentile. Temperatures for the three year period were warmer than average everywhere, but the warmest conditions continue to be in the southern counties.

The 48-month period has the upper, lower, and Little Colorado, lower Gila, and Salt near average and the other 10 watersheds below the 24^th percentile. Two watersheds, the San Simon and Santa Cruz, are below the 3^rd percentile. The 48 month period remains the warmest long term period, but only Maricopa and Pinal counties are above the 97^th percentile. Mohave and Gila counties are below the 68^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	21.62	CD1	66.96
Upper Colorado	53.85	CD2	68.26
Little Colorado	51.28	CD3	77.39
Verde	23.08	CD4	79.57
Bill Williams	15.38	CD5	80.87
Agua Fria	10.26	CD6	93.04
Lower Gila	35.90	CD7	92.17
Salt	23.08
Lower Colorado	30.77
Upper Gila	10.26
Santa Cruz	2.56
San Pedro	15.38
Willcox Playa	15.38
San Simon	2.56
White Water Draw	10.26

May 2009 - April 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	14.29	CD1	64.91
Upper Colorado	44.74	CD2	77.19
Little Colorado	34.21	CD3	80.70
Verde	21.05	CD4	67.54
Bill Williams	15.79	CD5	81.58
Agua Fria	10.53	CD6	97.37
Lower Gila	55.26	CD7	88.60
Salt	39.47
Lower Colorado	30.26
Upper Gila	23.68
Santa Cruz	2.63
San Pedro	15.79
Willcox Playa	15.79
San Simon	2.63
White Water Draw	15.79

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

May 2012 Arizona Drought Update (based on precipitation data through April 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

April had near average precipitation in 12 watersheds, slightly more precipitation than average in the Lower Colorado, and below average precipitation in the Virgin and White Water Draw watersheds. Two storm systems moved through Arizona, one in the middle of the month, and the other near the end of April. Most of the rainfall was down in Yuma County or across northern Arizona. The first system dropped some late snow on the higher elevations in northern Arizona. Other than the one cold storm in mid April, temperatures were well above average for all counties except Gila County, which was near average.

The 3-month period is still the driest short-term interval with all but three watersheds below the 29^th percentile, and five below the 17^th percentile. Three month temperatures were much warmer than average, above the 75^th percentile, in all counties except Gila.

The 6-month period precipitation was near average in all watersheds except the Verde and the Virgin watersheds, at the 30^th and 8^th percentile, respectively. Six month temperatures were slightly warmer than normal across the state.

The 12-month period was drier than average in 12 of the 15 watersheds, with the White Water Draw, upper and Little Colorado receiving near average precipitation. Temperatures were much warmer than average, above the 80^th percentile, in the southern two thirds of the state.

The 24-month period is still the driest long-term interval with all but two watersheds, the upper and Little Colorado, below the 18^th percentile. This is largely due to two consecutive La Niña winters where the few storms that crossed through Arizona passed over the upper Colorado and little Colorado watersheds. Temperatures for the last 2 years have been much warmer than average everywhere in the state, but warmest in the southern two thirds of Arizona.

The 36-month period has four watersheds with near average precipitation and three watersheds slightly drier than average. Eight watersheds are below the 16^th percentile and two of those are below the 3^rd percentile. Temperatures for the three year period were warmer than average everywhere, but the warmest conditions continue to be in the southern counties.

The 48-month period has the upper, lower, and Little Colorado, lower Gila, and Salt near average and the other 10 watersheds below the 24^th percentile. Two watersheds, the San Simon and Santa Cruz, are below the 3^rd percentile. The 48 month period remains the warmest long term period, but only Maricopa and Pinal counties are above the 97^th percentile. Mohave and Gila counties are below the 68^th percentile.