State Precipitation & Temperature Update for Arizona

Conditions through February 2009

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. Current update is 03/29/2009. The data are preliminary.

Precipitation Percentiles by Watershed (through February 2009)

Temperature Percentiles by Climate Division (through February 2009)

SHORT TERM CONDITIONS: 1-6 MONTHS

February precipitation was near or slightly above average across northern and western Arizona, and slightly below average in the southeastern watersheds. Temperatures were near or slightly above average in the northern half of the state, and significantly warmer than average in the southern half. The three-month period of December through February was wetter than average for all but the southeastern third of the state. The two driest watersheds, Santa Cruz and Willcox Playa were below the 25^th percentile. Temperatures for the three month period were near average in Gila County, slightly warmer than average along the western edge of the state, and well above average in the rest of the state. The six-month period precipitation was near average in the western half of the state, and in the Salt River basin. The Little Colorado River and the southeastern watersheds were drier than average, all below the 29^th percentile. Five watersheds were below the 23^rd percentile. Temperatures over the last six months were near average in Gila County, and well above average in all other counties. The warmest temperatures were in Yuma, Pinal and Maricopa counties, all above the 95^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	25.64	CD1	64.78
Upper Colorado	41.03	CD2	68.70
Little Colorado	43.59	CD3	59.57
Verde	61.54	CD4	46.09
Bill Williams	66.67	CD5	50.00
Agua Fria	57.69	CD6	80.43
Lower Gila	56.41	CD7	81.74
Salt	76.92
Lower Colorado	74.36
Upper Gila	35.90
Santa Cruz	38.46
San Pedro	38.46
Willcox Playa	26.32
San Simon	56.41
White Water Draw	25.64

FEBRUARY 2009: 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	35.14	CD1	73.04
Upper Colorado	73.68	CD2	79.13
Little Colorado	70.27	CD3	63.48
Verde	59.46	CD4	57.39
Bill Williams	60.53	CD5	70.87
Agua Fria	57.89	CD6	88.70
Lower Gila	60.53	CD7	80.43
Salt	76.32
Lower Colorado	71.05
Upper Gila	47.37
Santa Cruz	39.47
San Pedro	36.11
Willcox Playa	21.62
San Simon	57.89
White Water Draw	24.32

DECEMBER 2008 - FEBRUARY 2009 (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	15.71	CD1	79.13
Upper Colorado	47.37	CD2	85.22
Little Colorado	32.43	CD3	83.04
Verde	43.24	CD4	53.91
Bill Williams	44.74	CD5	95.65
Agua Fria	42.11	CD6	97.39
Lower Gila	42.11	CD7	75.65
Salt	57.89
Lower Colorado	56.58
Upper Gila	26.32
Santa Cruz	18.42
San Pedro	22.22
Willcox Playa	16.22
San Simon	28.95
White Water Draw	18.92

SEPTEMBER 2008 – FEBRUARY 2009 (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 precipitation was near or slightly below average in northwestern and southeastern Arizona, significantly below average on the Little Colorado River watershed, and very much above average in southwestern Arizona, and on the Salt River watershed. Gila County continues to be the only area with near average temperatures for the past year. The northern half of the state was warmer than average, between the 71^st and 81^st percentiles, but the southern half of the state was much warmer than average, above the 87^th percentile.

The 24 month period is still the wettest long-term period, with all watersheds, except the Virgin, Agua Fria and Santa Cruz, above the 40^th percentile. Three watersheds, the upper Colorado, lower Gila and Salt are above the 75^th percentile. Temperatures in all seven climate divisions are above the 76^th percentile, and five climate divisions are above the 87^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	2.78	CD1	71.93
Upper Colorado	44.74	CD2	75.44
Little Colorado	21.05	CD3	80.70
Verde	31.58	CD4	44.30
Bill Williams	34.21	CD5	95.61
Agua Fria	34.21	CD6	99.12
Lower Gila	81.58	CD7	87.72
Salt	65.79
Lower Colorado	60.53
Upper Gila	50.00
Santa Cruz	28.95
San Pedro	52.63
Willcox Playa	35.14
San Simon	60.53
White Water Draw	40.54

MARCH 2008 – FEBRUARY 2009 (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	2.86	CD1	76.99
Upper Colorado	75.68	CD2	88.50
Little Colorado	54.05	CD3	87.61
Verde	43.24	CD4	78.76
Bill Williams	45.95	CD5	93.81
Agua Fria	37.84	CD6	98.23
Lower Gila	81.08	CD7	96.46
Salt	81.08
Lower Colorado	62.16
Upper Gila	59.46
Santa Cruz	32.43
San Pedro	43.24
Willcox Playa	40.54
San Simon	70.27
White Water Draw	40.54

MARCH 2007 – FEBRUARY 2009 (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 very different between the northern and southern halves of the state. In northern Arizona, the upper Colorado and Little Colorado River watersheds had near average precipitation, while the Bill Williams, Verde and Agua Fria watersheds, had much lower than average precipitation. In southern Arizona, the upper and lower Gila, Salt and San Pedro watersheds were wetter than average, but the Santa Cruz was slightly drier than average. Six watersheds across the state were near average for precipitation. Temperatures over the three-year period remain extremely high with only the northwest climate division below the 87^th percentile, and the two southern climate divisions above the 98^th percentile.

The 48-month period continues to be the driest period, as the dry winter of 2008-2009 replaces the wet winter of 2004-2005. All watersheds except the Salt and lower Gila are below the 38^th percentile. Nine watersheds are below the 23^rd. The four-year temperatures continue to be extremely high, with the five climate divisions above the 90^th percentile, and southern third of the state above the 99^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	2.94	CD1	76.34
Upper Colorado	44.44	CD2	86.61
Little Colorado	52.78	CD3	89.29
Verde	36.11	CD4	83.04
Bill Williams	22.22	CD5	91.07
Agua Fria	27.78	CD6	98.21
Lower Gila	75.00	CD7	98.21
Salt	72.22
Lower Colorado	50.00
Upper Gila	66.67
Santa Cruz	33.33
San Pedro	63.89
Willcox Playa	58.33
San Simon	50.00
White Water Draw	52.78

MARCH 2006 – FEBRUARY 2009 (36-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	15.62	CD1	75.68
Upper Colorado	34.29	CD2	87.39
Little Colorado	22.86	CD3	90.09
Verde	11.43	CD4	90.09
Bill Williams	2.86	CD5	90.99
Agua Fria	2.86	CD6	99.10
Lower Gila	48.57	CD7	100.00
Salt	42.86
Lower Colorado	31.43
Upper Gila	28.57
Santa Cruz	5.71
San Pedro	20.00
Willcox Playa	22.86
San Simon	11.43
White Water Draw	37.14

MARCH 2005 – FEBRUARY 2009 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

March 2008 Arizona Drought Update based on precipitation data through February 2008)

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

SUMMARY

The 3-month period of December through February was wetter than average for all but the southeastern third of the state. The two driest watersheds, Santa Cruz and Willcox Playa were below the 25^th percentile. Temperatures for the three month period were near average in Gila County, slightly warmer than average along the western edge of the state, and well above average in the rest of the state.

The 6-month period precipitation was near average in the western half of the state, and in the Salt River basin. The Little Colorado River and the southeastern watersheds were drier than average, all below the 29^th percentile. Five watersheds were below the 23^rd percentile. Temperatures over the last six months were near average in Gila County, and well above average in all other counties. The warmest temperatures were in Yuma, Pinal and Maricopa counties, all above the 95^th percentile.