State Precipitation & Temperature Update for Arizona

Conditions through November 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. Not copied to summary yet – need to proof. Current update is 1/3/2010. The data are preliminary.

Precipitation Percentiles by Watershed (through November 2009)

Temperature Percentiles by Climate Division (through November 2009)

SHORT TERM CONDITIONS: 1-6 MONTHS

November precipitation was well below average across the western half of the state and slightly drier than average in much of eastern Arizona. The Willcox Playa and White Water Draw were near average and the Santa Cruz watershed was much wetter than average. Temperatures were much warmer than average (between the 85 and 95^th percentiles) across the entire state in November. This follows a very cool month in October. The three-month period, September through November, was much drier than average in all watersheds except the southernmost watersheds, which received near to slightly above average rainfall in September. Three-month temperatures have been slightly warmer than average on the Colorado Plateau and much warmer than average elsewhere. The six-month period precipitation, from June through November, was at the 36^th percentile in the lower Gila watershed, and below the 23^rd percentile in all other watersheds. The driest watersheds, the Upper Colorado, Bill Williams, Agua Fria, Verde and Salt, were below the 3^rd percentile. Six month temperatures were between the 60^th and 79^th percentiles in northern Arizona and above the 86^th percentile in the southern half of the state.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	21.05	CD1	87.83
Upper Colorado	20.51	CD2	88.7
Little Colorado	28.21	CD3	93.04
Verde	20.51	CD4	89.57
Bill Williams	17.95	CD5	89.57
Agua Fria	12.82	CD6	94.78
Lower Gila	17.95	CD7	85.65
Salt	15.38
Lower Colorado	10.26
Upper Gila	30.77
Santa Cruz	94.87
San Pedro	28.21
Willcox Playa	55.26
San Simon	15.38
White Water Draw	48.72

NOVEMBER 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	18.92	CD1	87.72
Upper Colorado	5.13	CD2	71.30
Little Colorado	20.51	CD3	73.91
Verde	7.69	CD4	80.43
Bill Williams	5.13	CD5	83.91
Agua Fria	5.13	CD6	91.30
Lower Gila	12.82	CD7	76.52
Salt	12.82
Lower Colorado	23.08
Upper Gila	20.51
Santa Cruz	38.46
San Pedro	17.95
Willcox Playa	44.74
San Simon	46.15
White Water Draw	43.59

SEPTEMBER 2009 - NOVEMBER 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	8.11	CD1	76.32
Upper Colorado	2.56	CD2	60.00
Little Colorado	5.13	CD3	78.26
Verde	2.56	CD4	88.70
Bill Williams	2.56	CD5	86.09
Agua Fria	2.56	CD6	95.65
Lower Gila	35.90	CD7	86.96
Salt	2.56
Lower Colorado	8.97
Upper Gila	20.51
Santa Cruz	23.08
San Pedro	17.95
Willcox Playa	21.05
San Simon	10.26
White Water Draw	15.79

JUNE 2009 – NOVEMBER 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 has been extremely dry with 10 watersheds below the 15^th percentile, three watersheds between the 18^th and 21^st percentiles, and two at the 26^th percentile. Temperatures were warmer than average in all climate divisions, with the warmest conditions in southern Arizona.

The 24-month period is the wettest short- and long-term period, with three watersheds above the 62^nd percentile, and eight watersheds below the 25^th percentile. The other four watersheds are between the 29^th and 44^th percentiles. Temperatures for the 24-month period are slightly warmer than average across northern Arizona, and very warm in Maricopa, Pinal, La Paz and Yuma counties.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	5.56	CD1	75.44
Upper Colorado	26.32	CD2	79.82
Little Colorado	7.89	CD3	84.21
Verde	10.53	CD4	79.82
Bill Williams	13.16	CD5	85.96
Agua Fria	10.53	CD6	99.12
Lower Gila	26.32	CD7	93.86
Salt	21.05
Lower Colorado	14.47
Upper Gila	7.89
Santa Cruz	7.89
San Pedro	7.89
Willcox Playa	18.42
San Simon	18.42
White Water Draw	7.89

DECEMBER 2009 – NOVEMBER 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	5.71	CD1	69.47
Upper Colorado	43.24	CD2	73.45
Little Colorado	29.73	CD3	83.19
Verde	18.92	CD4	64.60
Bill Williams	24.32	CD5	87.61
Agua Fria	21.62	CD6	98.23
Lower Gila	70.27	CD7	84.07
Salt	70.27
Lower Colorado	37.84
Upper Gila	43.24
Santa Cruz	18.92
San Pedro	18.92
Willcox Playa	18.92
San Simon	62.16
White Water Draw	21.62

DECEMBER 2007 – NOVEMBER 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 still a relatively “wet” interval with the lower Gila having above average precipitation, and the Salt having near average precipitation. The other 13 watersheds are still below the 34^th percentile, with 10 of them below the 25^th percentile. Climate division temperatures over the three-year period were all above the 74^th percentile and Pinal and Maricopa Counties had temperatures at the 100^th percentile, the warmest since 1895.

The 48-month period remains the driest long-term period. This period includes the winter of 2006, which was very dry statewide. All 15 watersheds are at or below the 38^th percentile, with 10 watersheds below the 20^th percentile and eight below the 15^th percentile. The four-year temperatures remain above the 87^th percentile everywhere except Mohave County, which was at the 77^th percentile. Maricopa and Pinal counties are at the 100th percentile, as the hottest 4-year period in the last 112 years.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	2.94	CD1	74.11
Upper Colorado	33.33	CD2	85.71
Little Colorado	16.67	CD3	87.95
Verde	8.33	CD4	81.25
Bill Williams	11.11	CD5	89.29
Agua Fria	8.33	CD6	100.00
Lower Gila	63.89	CD7	88.39
Salt	50.00
Lower Colorado	19.44
Upper Gila	30.56
Santa Cruz	8.33
San Pedro	16.67
Willcox Playa	22.22
San Simon	33.33
White Water Draw	25.00

DECEMBER 2006 – NOVEMBER 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	3.12	CD1	77.48
Upper Colorado	14.29	CD2	87.84
Little Colorado	11.43	CD3	90.99
Verde	5.71	CD4	87.39
Bill Williams	2.86	CD5	93.69
Agua Fria	2.86	CD6	100.00
Lower Gila	37.14	CD7	96.40
Salt	25.71
Lower Colorado	8.57
Upper Gila	28.57
Santa Cruz	11.43
San Pedro	20.00
Willcox Playa	28.57
San Simon	17.14
White Water Draw	31.43

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

December 2009 Arizona Drought Update (based on precipitation data through November 2009)

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, September through November, was much drier than average in all watersheds except the southernmost watersheds, which received near to slightly above average rainfall in September. Three-month temperatures have been slightly warmer than average on the Colorado Plateau and much warmer than average elsewhere.

The 6-month period precipitation, from June through November, was at the 36^th percentile in the lower Gila watershed, and below the 23^rd percentile in all other watersheds. The driest watersheds, the Upper Colorado, Bill Williams, Agua Fria, Verde and Salt, were below the 3^rd percentile. Six month temperatures were between the 60^th and 79^th percentiles in northern Arizona and above the 86^th percentile in the southern half of the state.