State Precipitation & Temperature Update for Arizona

Conditions through January 2010

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 2/28/2010. The data are preliminary.

Precipitation Percentiles by Watershed (through January 2010)

Temperature Percentiles by Climate Division (through January 2010)

SHORT TERM CONDITIONS: 1-6 MONTHS

January precipitation was well above average across the entire state with all watersheds above the 82^nd percentile, and 13 of 15 watersheds at or above the 95^th percentile. Surprisingly, temperatures were near or above average statewide, in spite of the series of winter storms that brought heavy rain and snow to all areas of Arizona. Western Arizona had temperatures above the 85^th percentile, while the eastern half of the state was near average for temperature. The three-month period, November through January, was also much wetter than average with all watersheds between the 63^rd ands 93^rd percentiles. The northwestern watersheds were the wettest, and the Santa Cruz and San Pedro were also above the 87^th percentile. Three-month temperatures were much cooler than average on the Colorado Plateau, and warmer than average throughout the rest of the state. The six-month period precipitation, from August through January, was wetter than average in the western watersheds and near average in the eastern watersheds. The driest watershed, the Little Colorado, was below the 32^nd percentile. Six month temperatures were cooler than average on the Colorado Plateau, and warmer than average elsewhere. The warmest counties were Maricopa and Pinal, at the 90^th percentile, and La Paz and Yuma at the 80^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	82.05	CD1	87.07
Upper Colorado	97.50	CD2	40.52
Little Colorado	97.44	CD3	75.00
Verde	95.00	CD4	62.93
Bill Williams	95.00	CD5	89.66
Agua Fria	97.50	CD6	90.52
Lower Gila	97.50	CD7	58.19
Salt	97.50
Lower Colorado	97.50
Upper Gila	97.50
Santa Cruz	95.00
San Pedro	97.50
Willcox Playa	95.00
San Simon	95.00
White Water Draw	89.74

JANUARY 2010: 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	70.27	CD1	74.35
Upper Colorado	92.31	CD2	38.70
Little Colorado	81.58	CD3	65.22
Verde	86.84	CD4	61.30
Bill Williams	89.74	CD5	78.26
Agua Fria	92.31	CD6	84.35
Lower Gila	82.05	CD7	62.61
Salt	84.62
Lower Colorado	92.31
Upper Gila	84.62
Santa Cruz	87.18
San Pedro	89.19
Willcox Playa	71.05
San Simon	82.05
White Water Draw	63.16

NOVEMBER 2009 - JANUARY 2010 (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	47.22	CD1	66.09
Upper Colorado	69.23	CD2	34.35
Little Colorado	31.58	CD3	73.04
Verde	55.26	CD4	65.22
Bill Williams	56.41	CD5	80.00
Agua Fria	66.67	CD6	90.43
Lower Gila	71.79	CD7	70.43
Salt	56.41
Lower Colorado	74.36
Upper Gila	48.72
Santa Cruz	53.85
San Pedro	56.76
Willcox Playa	44.74
San Simon	69.23
White Water Draw	42.11

AUGUST 2009 – JANUARY 2010 (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 remains the driest short term period, with 10 watersheds below the 39^th percentile, two below the 21^st percentile, and only one, the lower Gila, with above average precipitation. Temperatures were slightly warmer than average across the northern half of the state and much warmer than average in the southern counties.

The 24-month period is very dry with five watersheds below the 24^th percentile, three others between the 26^th and 28^th percentile, and only two watersheds, the lower Gila and Salt, wetter than average. Temperatures for the 24-month period are slightly warmer than average across northern Arizona, near average in Gila County and very warm in Maricopa and Pinal Counties, above the 98^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	13.51	CD1	72.17
Upper Colorado	51.28	CD2	63.48
Little Colorado	20.51	CD3	81.74
Verde	28.21	CD4	70.43
Bill Williams	35.90	CD5	86.09
Agua Fria	43.59	CD6	98.26
Lower Gila	66.67	CD7	83.04
Salt	38.46
Lower Colorado	58.97
Upper Gila	41.03
Santa Cruz	25.64
San Pedro	35.90
Willcox Playa	35.90
San Simon	35.90
White Water Draw	31.58

FEBRUARY 2009 – JANUARY 2010 (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	5.56	CD1	70.18
Upper Colorado	52.63	CD2	69.30
Little Colorado	18.42	CD3	82.02
Verde	23.68	CD4	57.46
Bill Williams	26.32	CD5	90.35
Agua Fria	28.95	CD6	99.12
Lower Gila	73.68	CD7	79.82
Salt	63.16
Lower Colorado	50.00
Upper Gila	50.00
Santa Cruz	21.05
San Pedro	42.11
Willcox Playa	26.32
San Simon	47.37
White Water Draw	21.05

FEBRUARY 2008 – JANUARY 2010 (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 “wettest” of the long term intervals, with only seven watersheds drier than average, six watersheds near average, and two watersheds wetter than average. Of the seven drier than average watersheds, only two are below the 25^th percentile. Climate division temperatures over the three-year period are all above the 81^st percentile, except Mohave County, slightly cooler at the 73^rd percentile. Pinal and Maricopa Counties continue to have temperatures at the 100^th percentile, the warmest since 1895.

The 48-month period remains the driest long-term period, although only slightly drier than the 24-month period. Nine watersheds are drier than average with four below the 20th percentile. Only one watershed, the lower Gila, is wetter than average at the 67^th percentile. The four-year temperatures continue to be quite warm, with all climate divisions above the 76^th percentile, and Maricopa and Pinal Counties at the 100th percentile, the hottest 4-year period since 1895.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	2.86	CD1	73.45
Upper Colorado	59.46	CD2	84.96
Little Colorado	43.24	CD3	88.05
Verde	32.43	CD4	81.42
Bill Williams	29.73	CD5	92.04
Agua Fria	32.43	CD6	100.00
Lower Gila	81.08	CD7	92.92
Salt	70.27
Lower Colorado	45.95
Upper Gila	59.46
Santa Cruz	24.32
San Pedro	40.54
Willcox Playa	29.73
San Simon	56.76
White Water Draw	27.03

FEBRUARY 2007 – JANUARY 2010 (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	3.03	CD1	76.11
Upper Colorado	41.67	CD2	86.61
Little Colorado	36.11	CD3	86.61
Verde	19.44	CD4	83.04
Bill Williams	8.33	CD5	91.07
Agua Fria	11.11	CD6	100.00
Lower Gila	66.67	CD7	93.75
Salt	58.33
Lower Colorado	33.33
Upper Gila	52.78
Santa Cruz	27.78
San Pedro	47.22
Willcox Playa	52.78
San Simon	38.89
White Water Draw	38.89

FEBRUARY 2006 – JANUARY 2010 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

February 2010 Arizona Drought Update (based on precipitation data through January 2010)

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, November through January, was also much wetter than average with all watersheds between the 63^rd ands 93^rd percentiles. The northwestern watersheds were the wettest, and the Santa Cruz and San Pedro were also above the 87^th percentile. Three-month temperatures were much cooler than average on the Colorado Plateau, and warmer than average throughout the rest of the state.

The 6-month period precipitation, from August through January, was wetter than average in the western watersheds and near average in the eastern watersheds. The driest watershed, the Little Colorado, was below the 32^nd percentile. Six month temperatures were cooler than average on the Colorado Plateau, and warmer than average elsewhere. The warmest counties were Maricopa and Pinal, at the 90^th percentile, and La Paz and Yuma at the 80^th percentile.