State Precipitation & Temperature Update for Arizona

Conditions through September 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 10/27/2010. The data are preliminary.

Precipitation Percentiles by Watershed (through September 2010)

Temperature Percentiles by Climate Division (through September 2010)

SHORT TERM CONDITIONS: 1-6 MONTHS

September precipitation was below average in all watersheds except the Salt River. The relative dryness was due to the early end to the monsoon. The southwestern corner of the state was the driest. Temperatures were much warmer than average in September. All counties were above the 88^th percentile, and Maricopa and Pinal counties were above the 95^th percentile. Again, this was attributable to the early end of the monsoon activity. High humidity kept nighttime temperatures high. The three-month period, reflecting the overall monsoon was better than a year ago. Five watersheds had below average summer rainfall while nine had above average rainfall. The Verde watershed had near average precipitation. Temperatures in the three-month period were also much warmer than average with all counties above the 85^th percentile, and the southern half of the state above the 97^th percentile. The six-month period, from April through September, had near average precipitation in six watersheds, with three above average and six below average. All counties had temperatures near or slightly above average, but the northern half of the state was between the 64^th and 71^st percentile, while the southern counties were above the 79^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	28.95	CD1	88.79
Upper Colorado	27.50	CD2	91.38
Little Colorado	55.00	CD3	88.79
Verde	35.00	CD4	90.52
Bill Williams	45.00	CD5	89.66
Agua Fria	7.50	CD6	95.69
Lower Gila	22.50	CD7	94.83
Salt	65.00
Lower Colorado	8.75
Upper Gila	35.00
Santa Cruz	27.50
San Pedro	32.50
Willcox Playa	40.00
San Simon	25.00
White Water Draw	40.00

SEPTEMBER 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	15.79	CD1	85.65
Upper Colorado	65.00	CD2	87.93
Little Colorado	92.50	CD3	89.66
Verde	52.50	CD4	88.79
Bill Williams	20.00	CD5	93.97
Agua Fria	35.00	CD6	98.28
Lower Gila	77.50	CD7	97.41
Salt	85.00
Lower Colorado	62.50
Upper Gila	72.50
Santa Cruz	32.50
San Pedro	80.00
Willcox Playa	67.50
San Simon	5.00
White Water Draw	66.67

JULY 2009 - SEPTEMBER 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	15.79	CD1	67.83
Upper Colorado	50.00	CD2	68.10
Little Colorado	77.50	CD3	63.79
Verde	27.50	CD4	64.66
Bill Williams	12.50	CD5	70.26
Agua Fria	10.00	CD6	80.17
Lower Gila	67.50	CD7	79.31
Salt	72.50
Lower Colorado	52.50
Upper Gila	52.50
Santa Cruz	17.50
San Pedro	60.00
Willcox Playa	50.00
San Simon	7.50
White Water Draw	53.85

APRIL 2009 – SEPTEMBER 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 is still the wettest short-term period statewide, with fourteen watersheds above the 40^th percentile, and only San Simon drier than average. Four watersheds are near average, and ten are wetter than average. This period had temperatures near average in five counties, and slightly above average in eight counties. Maricopa and Pinal counties were much warmer than average.

The 24-month period is no longer the driest long-term interval. It has ten watersheds drier than average, but only six are below the 22^nd percentile. The lower Gila and lower Colorado are the two wettest watersheds, above the 60^th percentile. The 24-month period was the coolest long-term period, with all climate divisions below the 95^th percentile. Three were below the 71^st percentile, with the warmest temperatures in the south.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	40.54	CD1	65.22
Upper Colorado	74.36	CD2	42.61
Little Colorado	61.54	CD3	56.52
Verde	53.85	CD4	56.96
Bill Williams	51.28	CD5	70.43
Agua Fria	61.54	CD6	81.74
Lower Gila	74.36	CD7	66.96
Salt	71.79
Lower Colorado	71.79
Upper Gila	64.10
Santa Cruz	56.41
San Pedro	79.49
Willcox Playa	68.42
San Simon	38.46
White Water Draw	64.10

OCTOBER 2009 – SEPTEMBER 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	14.29	CD1	70.18
Upper Colorado	52.63	CD2	67.11
Little Colorado	39.47	CD3	81.58
Verde	26.32	CD4	68.42
Bill Williams	31.58	CD5	81.14
Agua Fria	31.58	CD6	94.74
Lower Gila	63.16	CD7	84.65
Salt	55.26
Lower Colorado	60.53
Upper Gila	36.84
Santa Cruz	15.79
San Pedro	42.11
Willcox Playa	28.95
San Simon	15.79
White Water Draw	21.05

OCTOBER 2008 – SEPTEMBER 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 now the wettest of the long-term periods, with four watersheds wetter than average, upper Colorado, lower and upper Gila, and Salt, and seven drier than average. The driest are still the Virgin and Santa Cruz, both below the 25^th percentile. Four watersheds are near average. Temperatures have remained above average in all counties, with the southern half of the state above the 79^th percentile for temperature. Maricopa and Pinal County continue to be above the 96^th percentile.

The 48-month period is the driest interval, with only two watersheds having above average precipitation above the 61^st percentile. Six are below the 25^th percentile, and three of those are below the 15^th percentile. The four-year period continues to be the warmest interval, with all climate divisions above the 73^rd percentile, and five climate divisions above the 81^st percentile. Maricopa and Pinal Counties are above the 99^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	8.57	CD1	69.91
Upper Colorado	62.16	CD2	72.12
Little Colorado	43.24	CD3	79.65
Verde	27.03	CD4	67.26
Bill Williams	29.73	CD5	84.07
Agua Fria	32.43	CD6	96.46
Lower Gila	83.78	CD7	84.07
Salt	70.27
Lower Colorado	54.05
Upper Gila	62.16
Santa Cruz	24.32
San Pedro	56.76
Willcox Playa	32.43
San Simon	43.24
White Water Draw	32.43

OCTOBER 2007 – SEPTEMBER 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	73.21
Upper Colorado	61.11	CD2	81.25
Little Colorado	36.11	CD3	83.04
Verde	19.44	CD4	75.00
Bill Williams	13.89	CD5	86.16
Agua Fria	16.67	CD6	99.11
Lower Gila	75.00	CD7	88.84
Salt	55.56
Lower Colorado	38.89
Upper Gila	41.67
Santa Cruz	13.89
San Pedro	41.67
Willcox Playa	30.56
San Simon	25.00
White Water Draw	38.89

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

October 2010 Arizona Drought Update (based on precipitation data through September 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, reflecting the overall monsoon was better than a year ago. Five watersheds had below average summer rainfall while nine had above average rainfall. The Verde watershed had near average precipitation. Temperatures in the three-month period were also much warmer than average with all counties above the 85^th percentile, and the southern half of the state above the 97^th percentile.

The 6-month period, from April through September, had near average precipitation in six watersheds, with three above average and six below average. All counties had temperatures near or slightly above average, but the northern half of the state was between the 64^th and 71^st percentile, while the southern counties were above the 79^th percentile.