State Precipitation & Temperature Update for Arizona

Conditions through October 2008

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 11/27/2008. The data are preliminary.

Precipitation Percentiles by Watershed (through October 2008)

Temperature Percentiles by Climate Division (through October 2008)

SHORT TERM CONDITIONS: 1-6 MONTHS

October was dry everywhere in Arizona. The western watersheds were below the 15^th percentile, while all the eastern watersheds were below the 40^th percentile, except the San Pedro, which was at the 42^nd percentile for precipitation. Only two storm systems moved through the state in October, and the majority of rainfall fell in the southeast and eastern mountains. Temperatures were slightly above average, with the warmest temperatures in western Arizona. The three month period was drier than average in all but three watersheds. The upper and lower Gila and San Simon River watersheds all had above-average precipitation for the August through October period. Eleven watersheds were below the 40^th percentile and seven were below the 25^th percentile. The dry conditions kept temperatures above average in the western and northern parts of the state. The six-month period precipitation, from May through October, was wetter than average in the southern half of the state, and average or drier than average in the northern half of the state. This year the monsoon was very active in southern Arizona, and weak in northern Arizona. Six month temperatures were much warmer than average, above the 96^th percentile, in Maricopa and Pinal counties; above the 92^nd percentile in La Paz and Yuma Counties; above the 79^th percentile in Yavapai county, and below the 74^th percentile elsewhere.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	6.58	CD1	76.32
Upper Colorado	13.16	CD2	72.81
Little Colorado	28.95	CD3	78.95
Verde	10.53	CD4	69.74
Bill Williams	13.16	CD5	79.39
Agua Fria	10.53	CD6	85.53
Lower Gila	13.16	CD7	68.86
Salt	28.95
Lower Colorado	11.84
Upper Gila	18.42
Santa Cruz	13.16
San Pedro	42.11
Willcox Playa	15.79
San Simon	21.05
White Water Draw	18.42

OCTOBER 2008: 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	11.11	CD1	86.73
Upper Colorado	31.58	CD2	81.14
Little Colorado	10.53	CD3	86.84
Verde	18.42	CD4	71.49
Bill Williams	23.68	CD5	92.11
Agua Fria	15.79	CD6	92.98
Lower Gila	76.32	CD7	54.39
Salt	52.63
Lower Colorado	23.68
Upper Gila	65.79
Santa Cruz	28.95
San Pedro	39.47
Willcox Playa	21.05
San Simon	78.95
White Water Draw	26.32

AUGUST 2008 - OCTOBER 2008 (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	5.56	CD1	73.45
Upper Colorado	47.37	CD2	66.67
Little Colorado	36.84	CD3	79.82
Verde	44.74	CD4	41.67
Bill Williams	36.84	CD5	92.98
Agua Fria	39.47	CD6	96.49
Lower Gila	94.74	CD7	71.05
Salt	81.58
Lower Colorado	50.00
Upper Gila	89.47
Santa Cruz	68.42
San Pedro	89.47
Willcox Playa	60.53
San Simon	84.21
White Water Draw	54.05

MAY 2008 – OCTOBER 2008 (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 the wettest interval with 14 watersheds above the 40^th percentile, seven watersheds above the 67^th percentile, and three watersheds above the 83^rd percentile. The wettest watersheds were in southern Arizona. The Virgin watershed, in northwestern Arizona, was below the 9^th percentile. Temperatures continued to be warmer than average across the state, with the warmest conditions in the south.

The 24-month period has a large variation of conditions in the watersheds. Two watersheds are below the 14^th percentile, six are near the 50^th percentile, and one watershed is above the 80^th percentile. Temperatures for the 24-month period continue to be above the 75^th percentile across the state, with the coolest temperatures in Gila and Mohave counties, and the warmest temperatures in Maricopa, Pinal, and the southeastern counties.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	8.57	CD1	71.68
Upper Colorado	72.97	CD2	67.26
Little Colorado	45.95	CD3	77.88
Verde	45.95	CD4	70.80
Bill Williams	40.54	CD5	83.63
Agua Fria	48.65	CD6	88.50
Lower Gila	91.89	CD7	90.27
Salt	83.78
Lower Colorado	48.65
Upper Gila	81.08
Santa Cruz	67.57
San Pedro	67.57
Willcox Playa	55.56
San Simon	83.78
White Water Draw	56.76

NOVEMBER 2008 – OCTOBER 2008 (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	3.03	CD1	75.89
Upper Colorado	44.44	CD2	87.05
Little Colorado	30.56	CD3	90.18
Verde	19.44	CD4	83.04
Bill Williams	13.89	CD5	90.18
Agua Fria	16.67	CD6	95.54
Lower Gila	80.56	CD7	96.43
Salt	50.00
Lower Colorado	27.78
Upper Gila	50.00
Santa Cruz	22.22
San Pedro	44.44
Willcox Playa	33.33
San Simon	55.56
White Water Draw	47.22

NOVEMBER 2007 – OCTOBER 2008 (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 the driest long term period statewide, with the driest watersheds in west central Arizona. All but two watersheds are below the 41^st percentile, and seven watersheds are below the 23^rd percentile. Temperatures for the three year period continue to be very warm, with six of the seven climate divisions above the 89^th percentile, and two above the 98^th percentile. The southeast climate division continues to be the warmest 3-year period in 112 years.

The 48-month period has two watersheds (lower Gila and upper Colorado) wetter than average, seven watersheds near average, and six watersheds drier than average. The driest watersheds are the Santa Cruz in southeastern Arizona, and the Bill Williams in west central Arizona, both below the 23^rd percentile. The 48-month temperatures are still well above average in all climate divisions, with the southeastern division at the 100^th percentile, the warmest 48-month period since 1895.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	3.03	CD1	78.38
Upper Colorado	25.71	CD2	89.19
Little Colorado	17.14	CD3	89.19
Verde	11.43	CD4	91.89
Bill Williams	5.71	CD5	91.89
Agua Fria	11.43	CD6	98.20
Lower Gila	48.57	CD7	100.00
Salt	28.57
Lower Colorado	14.29
Upper Gila	37.14
Santa Cruz	22.86
San Pedro	40.00
Willcox Playa	42.86
San Simon	28.57
White Water Draw	40.00

NOVEMBER 2006 – OCTOBER 2008 (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	32.26	CD1	75.45
Upper Colorado	67.65	CD2	90.00
Little Colorado	41.18	CD3	88.18
Verde	41.18	CD4	91.82
Bill Williams	20.59	CD5	88.18
Agua Fria	32.35	CD6	98.18
Lower Gila	76.47	CD7	100.00
Salt	55.88
Lower Colorado	52.94
Upper Gila	50.00
Santa Cruz	20.59
San Pedro	38.24
Willcox Playa	41.18
San Simon	35.29
White Water Draw	52.94

NOVEMBER 2005 – OCTOBER 2008 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

November 2008 Arizona Drought Update (based on precipitation data through October 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 was drier than average in all but three watersheds. The upper and lower Gila and San Simon River watersheds all had above-average precipitation for the August through October period. Eleven watersheds were below the 40^th percentile and seven were below the 25^th percentile. The dry conditions kept temperatures above average in the western and northern parts of the state.

The 6-month period precipitation, from May through October, was wetter than average in the southern half of the state, and average or drier than average in the northern half of the state. This year the monsoon was very active in southern Arizona, and weak in northern Arizona. Six month temperatures were much warmer than average, above the 96^th percentile, in Maricopa and Pinal counties; above the 92^nd percentile in La Paz and Yuma Counties; above the 79^th percentile in Yavapai county, and below the 74^th percentile elsewhere.