State Precipitation & Temperature Update for Arizona

Conditions through June 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 7/28/2010. The data are preliminary.

Precipitation Percentiles by Watershed (through June 2010)

Temperature Percentiles by Climate Division (through June 2010)

SHORT TERM CONDITIONS: 1-6 MONTHS

June precipitation was below average for all watersheds except in the southwestern corner of the state. Three central Arizona watersheds, Verde, Salt, and Upper Gila, were between the 27^th and 37^th percentiles, but eight watersheds were at or below the 25^th percentile. Temperatures were warmer than average in June, due to the lack of monsoon thunderstorm activity. The three-month period, from April through June, is the driest period of all with only one watershed, the San Simon, wetter than average. Three watersheds in the SW are slightly drier than average, but eleven watersheds are at or below the 25^th percentile. Six of those watersheds are below the 15^th percentile. This is the result of a dry spring followed by a late start to the monsoon activity. Fortunately this period had near-average temperatures in most counties, and slightly cooler than average temperatures in Yavapai, La Paz, and Yuma counties. The six-month period precipitation, from January through June, remains the wettest period, with all watersheds above the 69^th percentile. Eleven watersheds are above the 77^th percentile. The precipitation in this period all fell between January and the end of March as the El Niño circulation steered winter storms across the state. The winter storms sent temperatures plummeting, particularly in the eastern half of the state. Only Mohave County had above average temperatures in the six month period.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	42.31	CD1	74.14
Upper Colorado	17.50	CD2	78.45
Little Colorado	25.00	CD3	68.97
Verde	27.50	CD4	63.79
Bill Williams	60.00	CD5	69.40
Agua Fria	18.75	CD6	84.05
Lower Gila	47.50	CD7	85.78
Salt	30.00
Lower Colorado	85.00
Upper Gila	37.50
Santa Cruz	15.00
San Pedro	10.00
Willcox Playa	25.00
San Simon	20.00
White Water Draw	16.25

JUNE 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	35.90	CD1	55.65
Upper Colorado	10.00	CD2	44.83
Little Colorado	17.50	CD3	36.21
Verde	7.50	CD4	53.02
Bill Williams	15.00	CD5	31.47
Agua Fria	7.50	CD6	47.41
Lower Gila	35.00	CD7	51.72
Salt	10.00
Lower Colorado	38.75
Upper Gila	17.50
Santa Cruz	25.00
San Pedro	22.50
Willcox Playa	17.50
San Simon	65.00
White Water Draw	12.50

APRIL 2009 - JUNE 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	71.05	CD1	65.22
Upper Colorado	90.00	CD2	34.05
Little Colorado	69.23	CD3	43.10
Verde	70.00	CD4	45.69
Bill Williams	77.50	CD5	45.69
Agua Fria	85.00	CD6	57.76
Lower Gila	92.50	CD7	38.79
Salt	82.50
Lower Colorado	87.50
Upper Gila	87.50
Santa Cruz	85.00
San Pedro	90.00
Willcox Playa	84.62
San Simon	87.50
White Water Draw	69.23

JANUARY 2009 – JUNE 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 precipitation still varies widely across the state. The Colorado River watersheds in western and northern Arizona were wetter than average, while the southeastern two-thirds of the state were near normal. The Colorado Plateau was much drier than average, the Little Colorado River basin was at the 15^th percentile. Whitewater Draw and the Willcox Playa in the southeast corner were at the 23^rd percentile. Temperatures in most counties were slightly warmer than average, but the Colorado Plateau was cooler than normal, which is somewhat unusual since it was also drier than normal.

The 24-month period was also quite variable with only two watersheds in central Arizona wetter than average, the Salt and lower Gila. The Colorado Plateau, including the Little Colorado and Verde watersheds, was much drier than normal, below the 24^th percentile. Six watersheds in northern and southeastern Arizona have had near average precipitation in the two year period. Temperatures for the 24-month period were warmer than average everywhere except Gila County. Yavapai, La Paz, Yuma, Maricopa and Pinal counties were all above the 79^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	44.59	CD1	65.22
Upper Colorado	64.10	CD2	37.39
Little Colorado	15.38	CD3	64.35
Verde	30.77	CD4	58.26
Bill Williams	41.03	CD5	66.96
Agua Fria	53.85	CD6	82.61
Lower Gila	69.23	CD7	63.04
Salt	46.15
Lower Colorado	69.23
Upper Gila	41.03
Santa Cruz	43.59
San Pedro	41.03
Willcox Playa	23.68
San Simon	43.59
White Water Draw	23.68

JULY 2009 – JUNE 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	16.67	CD1	70.18
Upper Colorado	57.89	CD2	68.42
Little Colorado	23.68	CD3	79.82
Verde	23.68	CD4	50.88
Bill Williams	34.21	CD5	83.33
Agua Fria	36.84	CD6	95.61
Lower Gila	71.05	CD7	74.56
Salt	60.53
Lower Colorado	57.89
Upper Gila	52.63
Santa Cruz	39.47
San Pedro	57.89
Willcox Playa	47.37
San Simon	50.00
White Water Draw	34.21

JULY 2008 – JUNE 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 still the wettest long term interval, but now only six watersheds are drier than average, five wetter than average, and three near average. The driest watersheds are in the northern half of the state, and are dry through all periods except the 6 month interval. These dry watersheds are the Little Colorado, Verde, Bill Williams and Agua Fria. The Little Colorado has been persistently dry while other watersheds have had some drought relief. Temperatures have remained above average in all counties, and the southern half of the state remains above the 79^th percentile for temperature. Maricopa and Pinal County continue to be above the 97^th percentile.

The 48-month period has the fewest watersheds (one) with above average precipitation, but it also has only six watersheds with below average precipitation. The wet winter of 2010 has improved a number of watersheds, although four remain below the 23^rd percentile. The four-year period continues to be the warmest interval, with all climate divisions above the 69^th percentile, and five climate divisions above the 79^th percentile. Maricopa and Pinal Counties remain above the 98^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	11.43	CD1	70.80
Upper Colorado	64.86	CD2	73.45
Little Colorado	35.14	CD3	79.65
Verde	35.14	CD4	65.49
Bill Williams	37.84	CD5	84.07
Agua Fria	35.14	CD6	97.35
Lower Gila	83.78	CD7	83.19
Salt	72.97
Lower Colorado	54.05
Upper Gila	62.16
Santa Cruz	40.54
San Pedro	43.24
Willcox Playa	32.43
San Simon	62.16
White Water Draw	27.03

JULY 2007 – JUNE 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	2.94	CD1	73.21
Upper Colorado	50.00	CD2	79.46
Little Colorado	33.33	CD3	82.14
Verde	22.22	CD4	69.64
Bill Williams	16.67	CD5	84.82
Agua Fria	19.44	CD6	98.21
Lower Gila	72.22	CD7	84.82
Salt	55.56
Lower Colorado	41.67
Upper Gila	58.33
Santa Cruz	33.33
San Pedro	55.56
Willcox Playa	58.33
San Simon	41.67
White Water Draw	47.22

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

July 2010 Arizona Drought Update (based on precipitation data through June 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

June precipitation was below average for all watersheds except in the southwestern corner of the state. Three central Arizona watersheds, Verde, Salt, and Upper Gila, were between the 27^th and 37^th percentiles, but eight watersheds were at or below the 25^th percentile. Temperatures were warmer than average in June, due to the lack of monsoon thunderstorm activity.

The 3-month period, from April through June, is the driest period of all with only one watershed, the San Simon, wetter than average. Three watersheds in the SW are slightly drier than average, but eleven watersheds are at or below the 25^th percentile. Six of those watersheds are below the 15^th percentile. This is the result of a dry spring followed by a late start to the monsoon activity. Fortunately this period had near-average temperatures in most counties, and slightly cooler than average temperatures in Yavapai, La Paz, and Yuma counties.

The 6-month period precipitation, from January through June, remains the wettest period, with all watersheds above the 69^th percentile. Eleven watersheds are above the 77^th percentile. The precipitation in this period all fell between January and the end of March as the El Niño circulation steered winter storms across the state. The winter storms sent temperatures plummeting, particularly in the eastern half of the state. Only Mohave County had above average temperatures in the six month period.

The 12-month period precipitation still varies widely across the state. The Colorado River watersheds in western and northern Arizona were wetter than average, while the southeastern two-thirds of the state were near normal. The Colorado Plateau was much drier than average, the Little Colorado River basin was at the 15^th percentile. Whitewater Draw and the Willcox Playa in the southeast corner were at the 23^rd percentile. Temperatures in most counties were slightly warmer than average, but the Colorado Plateau was cooler than normal, which is somewhat unusual since it was also drier than normal.

The 24-month period was also quite variable with only two watersheds in central Arizona wetter than average, the Salt and lower Gila. The Colorado Plateau, including the Little Colorado and Verde watersheds, was much drier than normal, below the 24^th percentile. Six watersheds in northern and southeastern Arizona have had near average precipitation in the two year period. Temperatures for the 24-month period were warmer than average everywhere except Gila County. Yavapai, La Paz, Yuma, Maricopa and Pinal counties were all above the 79^th percentile.

The 36-month period is still the wettest long term interval, but now only six watersheds are drier than average, five wetter than average, and three near average. The driest watersheds are in the northern half of the state, and are dry through all periods except the 6 month interval. These dry watersheds are the Little Colorado, Verde, Bill Williams and Agua Fria. The Little Colorado has been persistently dry while other watersheds have had some drought relief. Temperatures have remained above average in all counties, and the southern half of the state remains above the 79^th percentile for temperature. Maricopa and Pinal County continue to be above the 97^th percentile.

The 48-month period has the fewest watersheds (one) with above average precipitation, but it also has only six watersheds with below average precipitation. The wet winter of 2010 has improved a number of watersheds, although four remain below the 23^rd percentile. The four-year period continues to be the warmest interval, with all climate divisions above the 69^th percentile, and five climate divisions above the 79^th percentile. Maricopa and Pinal Counties remain above the 98^th percentile.