State Precipitation & Temperature Update for Arizona

Conditions through March 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 04/29/2009. The data are preliminary.

Precipitation Percentiles by Watershed (through March 2009)

Temperature Percentiles by Climate Division (through March 2009)

SHORT TERM CONDITIONS: 1-6 MONTHS

March precipitation was below the 24^th percentile everywhere in the state except the far southeast corner. Only Willcox and Whitewater Draw watersheds had above average precipitation for March. Nine watersheds were below the 13^th percentile. Temperatures were above average for the month, but only the southern climate divisions were above the 88^th percentile. Several cold fronts moved through the state in march, but very little moisture was available, so conditions remained dry statewide. The three-month period of January through March was also much drier than average statewide because March was exceptionally dry, February was also relatively dry, and January had only a few wet storms. All watersheds were below the 29^th percentile and nine were below the 21^st percentile. Temperatures for the three month period were well above average in all climate divisions. The six-month period precipitation was near average in the northern half of the state, except the Virgin River watershed which continues to be exceptionally dry, and much drier than average in the southern half, below the 29^th percentile. Temperatures over the last six months were slightly above 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	7.69	CD1	72.17
Upper Colorado	17.95	CD2	81.74
Little Colorado	17.95	CD3	71.74
Verde	12.82	CD4	83.04
Bill Williams	7.69	CD5	67.39
Agua Fria	10.26	CD6	89.57
Lower Gila	10.26	CD7	88.70
Salt	10.26
Lower Colorado	8.97
Upper Gila	23.08
Santa Cruz	10.26
San Pedro	23.08
Willcox Playa	61.54
San Simon	6.41
White Water Draw	64.10

MARCH 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	14.47	CD1	83.33
Upper Colorado	17.95	CD2	86.96
Little Colorado	15.79	CD3	85.65
Verde	17.95	CD4	78.07
Bill Williams	28.21	CD5	82.61
Agua Fria	17.95	CD6	95.65
Lower Gila	15.38	CD7	92.17
Salt	25.64
Lower Colorado	28.21
Upper Gila	15.38
Santa Cruz	17.95
San Pedro	20.51
Willcox Playa	28.95
San Simon	15.38
White Water Draw	28.95

JANUARY 2008 - MARCH 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	13.89	CD1	77.39
Upper Colorado	44.74	CD2	85.22
Little Colorado	43.24	CD3	82.61
Verde	43.24	CD4	66.09
Bill Williams	44.74	CD5	86.09
Agua Fria	44.74	CD6	95.65
Lower Gila	31.58	CD7	87.83
Salt	52.63
Lower Colorado	59.21
Upper Gila	23.68
Santa Cruz	15.79
San Pedro	22.22
Willcox Playa	16.22
San Simon	21.05
White Water Draw	18.92

OCTOBER 2008 – MARCH 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 northern and southeastern Arizona, and above average on the Salt, lower Gila and lower Colorado River watersheds. Gila County continues to be the only area with near average temperatures for the past year. The northern half of the state was slightly warmer than average, between the 72^nd and 84^th percentiles, but the southern half of the state was much warmer than average, above the 85^th percentile.

The 24 month period is still the wettest long-term period, with five watersheds below average and four watersheds above the 62^nd 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 75^th percentile, and the southern half of the state is above the 95^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	2.78	CD1	72.81
Upper Colorado	42.11	CD2	74.56
Little Colorado	26.32	CD3	83.33
Verde	31.58	CD4	46.05
Bill Williams	39.47	CD5	93.86
Agua Fria	31.58	CD6	99.12
Lower Gila	73.68	CD7	85.96
Salt	68.42
Lower Colorado	60.53
Upper Gila	57.89
Santa Cruz	28.95
San Pedro	55.26
Willcox Playa	37.84
San Simon	55.26
White Water Draw	43.24

APRIL 2008 – MARCH 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	75.22
Upper Colorado	62.16	CD2	89.38
Little Colorado	45.95	CD3	86.73
Verde	37.84	CD4	79.65
Bill Williams	43.24	CD5	92.92
Agua Fria	29.73	CD6	100.00
Lower Gila	78.38	CD7	95.58
Salt	70.27
Lower Colorado	54.05
Upper Gila	48.65
Santa Cruz	29.73
San Pedro	37.84
Willcox Playa	40.54
San Simon	62.16
White Water Draw	37.84

APRIL 2007 – MARCH 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 drier than average across northern and southern Arizona and wetter than average across central Arizona. Only the Salt, lower Gila and lower Colorado River watersheds have had above average precipitation over the past three years, but six watersheds had near average 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 97^th percentile.

The 48-month period continues to be the driest long term period, as the very dry winter of 2008-2009 replaces the very wet winter of 2004-2005. All watersheds except the Salt, lower Gila and Whitewater Draw are below the 37^th percentile. Nine watersheds are below the 32^nd percentile. The four-year temperatures continue to be extremely high, with six climate divisions above the 87^th percentile, and the southern third of the state above the 100^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	2.94	CD1	77.68
Upper Colorado	36.11	CD2	87.50
Little Colorado	47.22	CD3	90.18
Verde	30.56	CD4	84.82
Bill Williams	19.44	CD5	93.75
Agua Fria	16.67	CD6	99.11
Lower Gila	69.44	CD7	97.32
Salt	63.89
Lower Colorado	44.44
Upper Gila	61.11
Santa Cruz	30.56
San Pedro	58.33
Willcox Playa	58.33
San Simon	41.67
White Water Draw	55.56

APRIL 2006 – MARCH 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	6.25	CD1	75.68
Upper Colorado	25.71	CD2	87.39
Little Colorado	22.86	CD3	89.19
Verde	14.29	CD4	91.89
Bill Williams	2.86	CD5	90.09
Agua Fria	2.86	CD6	100.00
Lower Gila	40.00	CD7	100.00
Salt	34.29
Lower Colorado	28.57
Upper Gila	25.71
Santa Cruz	8.57
San Pedro	22.86
Willcox Playa	31.43
San Simon	14.29
White Water Draw	37.14

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

April 2008 Arizona Drought Update based on precipitation data through March 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 January through March was also much drier than average statewide because March was exceptionally dry, February was also relatively dry, and January had only a few wet storms. All watersheds were below the 29^th percentile and nine were below the 21^st percentile. Temperatures for the three month period were well above average in all climate divisions

The 6-month period precipitation was near average in the northern half of the state, except the Virgin River watershed which continues to be exceptionally dry, and much drier than average in the southern half, below the 29^th percentile. Temperatures over the last six months were slightly above 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.