State Precipitation & Temperature Update for Arizona

Conditions through October 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. Current update is 11/24/2009. The data are preliminary.

Precipitation Percentiles by Watershed (through October 2009)

Temperature Percentiles by Climate Division (through October 2009)

SHORT TERM CONDITIONS: 1-6 MONTHS

October precipitation was well below average in all but three watersheds, the Verde, Willcox Playa and Whitewater Draw. Only three weak storms moved through Arizona in October, and there was very little moisture available for precipitation. The storms did bring very cold temperatures, and parts of the Mogollon Rim had 1 to 3 inches of snow during the last storm of the month. Temperatures were near average in four climate divisions, and well below average in three others. The three-month period of August through October includes the tail end of the monsoon, and it is the driest of our short-term drought indicators. Only three watersheds were above the 27^th percentile, while 10 watersheds were below the 13^th percentile for precipitation. Temperatures for the three-month period were near average in two climate divisions in the northeast, and between the 77^th and 84^th percentiles in five climate divisions. During the six-month period only the lower Gila has received near average precipitation. Ten watersheds are below the 21^st percentile, with the driest conditions in the northern half of the state, plus the Santa Cruz and San Pedro watersheds. However, even the southeastern watersheds are all below the 36^th percentile. Those watersheds normally receive the majority of their annual rainfall during the monsoon, and this summer was exceedingly dry. Temperatures over the last six months were again above average statewide, with the coolest climate divisions on the Colorado Plateau between the 70^th and 75^th percentiles.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	15.38	CD1	46.96
Upper Colorado	12.82	CD2	30.43
Little Colorado	17.95	CD3	23.91
Verde	51.28	CD4	58.26
Bill Williams	15.38	CD5	34.78
Agua Fria	12.82	CD6	43.48
Lower Gila	15.38	CD7	53.91
Salt	15.38
Lower Colorado	12.82
Upper Gila	23.08
Santa Cruz	15.38
San Pedro	38.46
Willcox Playa	43.59
San Simon	69.23
White Water Draw	53.85

OCTOBER 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	27.03	CD1	78.07
Upper Colorado	2.56	CD2	50.87
Little Colorado	5.13	CD3	61.74
Verde	10.26	CD4	83.48
Bill Williams	2.56	CD5	80.00
Agua Fria	5.13	CD6	79.57
Lower Gila	41.03	CD7	77.39
Salt	5.13
Lower Colorado	10.26
Upper Gila	12.82
Santa Cruz	5.13
San Pedro	10.26
Willcox Playa	15.38
San Simon	38.46
White Water Draw	23.08

AUGUST 2008 - OCTOBER 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	13.51	CD1	74.56
Upper Colorado	20.51	CD2	70.43
Little Colorado	10.26	CD3	86.96
Verde	12.82	CD4	86.09
Bill Williams	5.13	CD5	93.04
Agua Fria	5.13	CD6	96.52
Lower Gila	58.97	CD7	88.70
Salt	12.82
Lower Colorado	12.82
Upper Gila	28.21
Santa Cruz	5.13
San Pedro	20.51
Willcox Playa	35.90
San Simon	29.49
White Water Draw	26.32

MAY 2008 – OCTOBER 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 precipitation was below average in all fifteen watersheds with eleven watersheds below the 22^nd percentile and seven watersheds remaining below the 17^th percentile. The driest watersheds are in the southeast, and across north central Arizona. During the past 12 months, temperatures have been above the 78^th percentile everywhere except the northwest. The southern half of the state has had the greatest departure from average temperatures.

The 24 month period is the wettest of both the short and long-term periods. The Salt, San Simon, and Lower Gila watersheds have all received above average precipitation during the past 2 years, most of that received a year ago during a very wet monsoon. Two other watersheds, the upper Gila and upper Colorado, were near average. Seven watersheds were below the 25^th percentile and three were between the 27^th and 36^th percentiles. Temperatures over the past two years were below the 71^st percentile in Gila and Mohave Counties, but above the 78^th percentile in the rest of the state.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	5.56	CD1	74.56
Upper Colorado	28.95	CD2	79.82
Little Colorado	13.16	CD3	83.77
Verde	18.42	CD4	78.95
Bill Williams	21.05	CD5	86.40
Agua Fria	18.42	CD6	97.37
Lower Gila	31.58	CD7	92.11
Salt	36.84
Lower Colorado	35.53
Upper Gila	10.53
Santa Cruz	2.63
San Pedro	7.89
Willcox Playa	16.22
San Simon	21.05
White Water Draw	10.53

NOVEMBER 2008 – OCTOBER 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	5.88	CD1	70.80
Upper Colorado	48.65	CD2	78.76
Little Colorado	24.32	CD3	84.07
Verde	27.03	CD4	69.91
Bill Williams	21.62	CD5	89.38
Agua Fria	21.62	CD6	96.46
Lower Gila	78.38	CD7	86.28
Salt	72.97
Lower Colorado	35.14
Upper Gila	40.54
Santa Cruz	16.22
San Pedro	29.73
Willcox Playa	24.32
San Simon	64.86
White Water Draw	21.62

NOVEMBER 2007 – OCTOBER 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 also a relatively “wet” interval since one watershed, the lower Gila, had above average precipitation and one watershed, the Salt, had near average precipitation. The other 13 watersheds are below the 34^th percentile, and 11 of them are below the 25^th percentile. Climate division temperatures over the three-year period were all above the 75^th percentile and Pinal and Maricopa Counties had temperatures at the 99^th percentile.

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 37^th percentile, with 12 watersheds below the 25 percentile and four below the 4^th percentile. The four-year temperatures remain above the 89^th percentile everywhere except Mohave County, which was at the 76^th percentile. Excluding Yuma and La Paz Counties, the entire southern third of the state was at the 99^th or 100 percentile, as the hottest 4-year period in the last 112 years.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	2.94	CD1	75.00
Upper Colorado	30.56	CD2	85.71
Little Colorado	16.67	CD3	87.50
Verde	13.89	CD4	82.59
Bill Williams	11.11	CD5	90.18
Agua Fria	13.89	CD6	99.11
Lower Gila	63.89	CD7	93.75
Salt	47.22
Lower Colorado	22.22
Upper Gila	22.22
Santa Cruz	2.78
San Pedro	13.89
Willcox Playa	25.00
San Simon	33.33
White Water Draw	22.22

NOVEMBER 2006 – OCTOBER 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	75.68
Upper Colorado	17.14	CD2	89.19
Little Colorado	8.57	CD3	89.64
Verde	11.43	CD4	89.19
Bill Williams	2.86	CD5	92.79
Agua Fria	2.86	CD6	100.00
Lower Gila	37.14	CD7	99.10
Salt	25.71
Lower Colorado	8.57
Upper Gila	22.86
Santa Cruz	2.86
San Pedro	20.00
Willcox Playa	28.57
San Simon	17.14
White Water Draw	22.86

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

November 2009 Arizona Drought Update based on precipitation data through October 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

October precipitation was well below average in all but three watersheds, the Verde, Willcox Playa and Whitewater Draw. Only three weak storms moved through Arizona in October, and there was very little moisture available for precipitation. The storms did bring very cold temperatures, and parts of the Mogollon Rim had 1 to 3 inches of snow during the last storm of the month. Temperatures were near average in four climate divisions, and well below average in three others.

The 3-month period of August through October includes the tail end of the monsoon, and it is the driest of our short-term drought indicators. Only three watersheds were above the 27^th percentile, while 10 watersheds were below the 13^th percentile for precipitation. Temperatures for the three-month period were near average in two climate divisions in the northeast, and between the 77^th and 84^th percentiles in five climate divisions.

During the six-month period only the lower Gila has received near average precipitation. Ten watersheds are below the 21^st percentile, with the driest conditions in the northern half of the state, plus the Santa Cruz and San Pedro watersheds. However, even the southeastern watersheds are all below the 36^th percentile. Those watersheds normally receive the majority of their annual rainfall during the monsoon, and this summer was exceedingly dry. Temperatures over the last six months were again above average statewide, with the coolest climate divisions on the Colorado Plateau between the 70^th and 75^th percentiles.

The 12-month period precipitation was below average in all fifteen watersheds with eleven watersheds below the 22^nd percentile and seven watersheds remaining below the 17^th percentile. The driest watersheds are in the southeast, and across north central Arizona. During the past 12 months, temperatures have been above the 78^th percentile everywhere except the northwest. The southern half of the state has had the greatest departure from average temperatures.

The 24 month period is the wettest of both the short and long-term periods. The Salt, San Simon, and Lower Gila watersheds have all received above average precipitation during the past 2 years, most of that received a year ago during a very wet monsoon. Two other watersheds, the upper Gila and upper Colorado, were near average. Seven watersheds were below the 25^th percentile and three were between the 27^th and 36^th percentiles. Temperatures over the past two years were below the 71^st percentile in Gila and Mohave Counties, but above the 78^th percentile in the rest of the state.

The 36-month period is also a relatively “wet” interval since one watershed, the lower Gila, had above average precipitation and one watershed, the Salt, had near average precipitation. The other 13 watersheds are below the 34^th percentile, and 11 of them are below the 25^th percentile. Climate division temperatures over the three-year period were all above the 75^th percentile and Pinal and Maricopa Counties had temperatures at the 99^th percentile.

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 37^th percentile, with 12 watersheds below the 25 percentile and four below the 4^th percentile. The four-year temperatures remain above the 89^th percentile everywhere except Mohave County, which was at the 76^th percentile. Excluding Yuma and La Paz Counties, the entire southern third of the state was at the 99^th or 100 percentile, as the hottest 4-year period in the last 112 years.