State Precipitation & Temperature Update for Arizona

Conditions through March 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 4/12/2012. The data are preliminary.

Precipitation Percentiles by Watershed (through March 2012)

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Temperature Percentiles by Climate Division (through March 2012)

SHORT TERM CONDITIONS: 1-6 MONTHS

March had near or slightly below average precipitation in 13 watersheds and slightly more precipitation than average in the Bill Williams and Agua Fria watersheds. Two weak storms moved through in the beginning of the month and a strong winter storm passed through around the 18^th. The southern counties were only slightly warmer than average, while Mohave, Coconino, Navajo and Apache counties were much warmer than average. The three month period was the driest short-term interval with all 15 watersheds below the 22^nd percentile, and eleven below the 20^th percentile. Three month temperatures were much warmer than average, above the 80^th percentile, in all counties except Gila. Six month precipitation was near average in all watersheds except the Little Colorado, Santa Cruz and San Simon watersheds, all between the 20^th and 30^th percentiles. The Virgin watershed was at the 18^th percentile. Six month temperatures were near or slightly warmer than normal across the state.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	29.76	CD1	78.81
Upper Colorado	33.33	CD2	77.12
Little Colorado	33.33	CD3	64.83
Verde	42.86	CD4	68.64
Bill Williams	64.29	CD5	62.71
Agua Fria	66.67	CD6	72.03
Lower Gila	38.10	CD7	64.41
Salt	33.33
Lower Colorado	33.33
Upper Gila	33.33
Santa Cruz	33.33
San Pedro	33.33
Willcox Playa	38.10
San Simon	47.62
White Water Draw	35.71

MARCH 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	21.95	CD1	83.76
Upper Colorado	19.05	CD2	84.75
Little Colorado	17.07	CD3	80.08
Verde	14.29	CD4	72.03
Bill Williams	21.43	CD5	84.75
Agua Fria	21.43	CD6	88.98
Lower Gila	11.90	CD7	81.36
Salt	14.29
Lower Colorado	9.52
Upper Gila	16.67
Santa Cruz	11.90
San Pedro	14.29
Willcox Playa	19.51
San Simon	19.05
White Water Draw	21.95

JANUARY 2012 - MARCH 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	17.95	CD1	71.19
Upper Colorado	31.71	CD2	53.39
Little Colorado	47.50	CD3	54.24
Verde	37.50	CD4	58.47
Bill Williams	43.90	CD5	68.64
Agua Fria	41.46	CD6	79.66
Lower Gila	36.59	CD7	72.46
Salt	36.59
Lower Colorado	26.83
Upper Gila	36.59
Santa Cruz	26.83
San Pedro	25.64
Willcox Playa	32.50
San Simon	43.90
White Water Draw	40.00

OCTOBER 2011 – MARCH 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 10 of the 15 watersheds, with the White Water Draw, San Pedro, Lower Gila, upper and Little Colorado receiving near average precipitation. Temperatures were much warmer than average, above the 75^th percentile, in the southern two thirds of the state.

The 24-month period is the driest long-term interval with all but two watersheds, the upper and Little Colorado, below the 19^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	62.39
Upper Colorado	36.59	CD2	57.26
Little Colorado	48.78	CD3	75.21
Verde	21.95	CD4	82.91
Bill Williams	24.39	CD5	81.20
Agua Fria	24.39	CD6	88.89
Lower Gila	31.71	CD7	88.89
Salt	21.95
Lower Colorado	14.63
Upper Gila	26.83
Santa Cruz	12.20
San Pedro	31.71
Willcox Playa	27.50
San Simon	14.63
White Water Draw	35.00

APRIL 2011 - MARCH 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	18.42	CD1	64.66
Upper Colorado	35.00	CD2	65.95
Little Colorado	50.00	CD3	74.14
Verde	17.50	CD4	81.03
Bill Williams	10.00	CD5	79.31
Agua Fria	2.50	CD6	88.79
Lower Gila	12.50	CD7	90.52
Salt	15.00
Lower Colorado	10.00
Upper Gila	7.50
Santa Cruz	2.50
San Pedro	10.00
Willcox Playa	12.50
San Simon	2.50
White Water Draw	15.00

APRIL 2010 - MARCH 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 three watersheds with near average precipitation and three watersheds slightly drier than average. Nine watersheds are below the 19^th percentile and two of those are below the 6^th percentile. Temperatures for the three year period were warmer than average everywhere, but the warmest conditions were in the southern counties.

The 48-month period has the upper Colorado, lower Gila, and Salt near average and the other 12 watersheds below the 29^th percentile. Two watersheds, the San Simon and San Pedro, 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 96^th percentile. All the northern counties are below the 73^rd percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	18.92	CD1	67.83
Upper Colorado	53.85	CD2	60.00
Little Colorado	48.72	CD3	77.39
Verde	20.51	CD4	79.13
Bill Williams	15.38	CD5	79.13
Agua Fria	10.26	CD6	92.17
Lower Gila	41.03	CD7	88.70
Salt	28.21
Lower Colorado	23.08
Upper Gila	10.26
Santa Cruz	5.13
San Pedro	15.38
Willcox Playa	15.38
San Simon	2.56
White Water Draw	10.26

APRIL 2009 - MARCH 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	65.79
Upper Colorado	44.74	CD2	73.68
Little Colorado	28.95	CD3	78.07
Verde	15.79	CD4	64.91
Bill Williams	13.16	CD5	82.46
Agua Fria	13.16	CD6	96.49
Lower Gila	52.63	CD7	86.84
Salt	39.47
Lower Colorado	26.32
Upper Gila	23.68
Santa Cruz	2.63
San Pedro	15.79
Willcox Playa	15.79
San Simon	2.63
White Water Draw	18.42

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

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

March had near or slightly below average precipitation in 13 watersheds and slightly more precipitation than average in the Bill Williams and Agua Fria watersheds. Two weak storms moved through in the beginning of the month and a strong winter storm passed through around the 18^th. The southern counties were only slightly warmer than average, while Mohave, Coconino, Navajo and Apache counties were much warmer than average.

The 3-month period was the driest short-term interval with all 15 watersheds below the 22^nd percentile, and eleven below the 20^th percentile. Three month temperatures were much warmer than average, above the 80^th percentile, in all counties except Gila.

The 6-month period precipitation was near average in all watersheds except the Little Colorado, Santa Cruz and San Simon watersheds, all between the 20^th and 30^th percentiles. The Virgin watershed was at the 18^th percentile. Six month temperatures were near or slightly warmer than normal across the state.

The 12-month period was drier than average in 10 of the 15 watersheds, with the White Water Draw, San Pedro, Lower Gila, upper and Little Colorado receiving near average precipitation. Temperatures were much warmer than average, above the 75^th percentile, in the southern two thirds of the state.

The 24-month period is the driest long-term interval with all but two watersheds, the upper and Little Colorado, below the 19^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 has three watersheds with near average precipitation and three watersheds slightly drier than average. Nine watersheds are below the 19^th percentile and two of those are below the 6^th percentile. Temperatures for the three year period were warmer than average everywhere, but the warmest conditions were in the southern counties.

The 48-month period has the upper Colorado, lower Gila, and Salt near average and the other 12 watersheds below the 29^th percentile. Two watersheds, the San Simon and San Pedro, 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 96^th percentile. All the northern counties are below the 73^rd percentile.