State Precipitation & Temperature Update for Arizona

Conditions through October 2007

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 12/02/2007. The data are preliminary.

Precipitation Percentiles by Watershed (through October 2007)

Temperature Percentiles by Climate Division (through October 2007)

SHORT TERM CONDITIONS: 1-6 MONTHS

October was extremely dry, with all watersheds, except the lower Colorado, below the 22^nd percentile. The lower Colorado typically receives almost no rainfall in October, so their percentile was almost average. For the second month in a row, temperatures were somewhat cooler than previous months. The northern counties were below the 70^th percentile and the warmest, in the southeast, were between the 76^th and 85^th percentile. The lack of fall rainfall will impact the spring run-off, as dry soil tends to absorb the snowmelt, reducing the flow into the reservoirs. The 3-month period of August through October, was near average on the upper Colorado, but below average everywhere else, because the tail end of the monsoon was fairly dry, and the fall has been dry as well. The clear skies and dry weather have pushed the temperatures above the 81^st percentile everywhere in the state. Maricopa and Pinal counties were the warmest and Yavapai County was the coolest. The 6-month period rainfall was near average for much of the state, and below average in the south central watersheds. The lower Gila had slightly above average rainfall in the past 6 months, due to heavy July precipitation in Gila Bend, Laveen, and Wickenburg. Temperatures in the northern and western part of the state were around the 93^rd percentile, and in the southeastern part of the state the temperatures were between the 95^th and 98^th percentile. Some early frontal systems brought cooler weather to the higher elevations, and the first freezing temperature was reported in September, and nighttime temperatures have dropped below freezing regularly at the higher elevations.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	5.41	CD1	65.93
Upper Colorado	10.81	CD2	69.47
Little Colorado	16.22	CD3	56.64
Verde	10.81	CD4	84.51
Bill Williams	21.62	CD5	61.95
Agua Fria	10.81	CD6	82.30
Lower Gila	13.51	CD7	76.99
Salt	13.51
Lower Colorado	45.95
Upper Gila	10.81
Santa Cruz	16.22
San Pedro	13.51
Willcox Playa	18.92
San Simon	13.51
White Water Draw	16.22

OCTOBER 2007: 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	2.86	CD1	87.17
Upper Colorado	48.65	CD2	85.84
Little Colorado	32.43	CD3	81.86
Verde	32.43	CD4	93.81
Bill Williams	21.62	CD5	85.40
Agua Fria	8.11	CD6	95.58
Lower Gila	35.14	CD7	87.61
Salt	18.92
Lower Colorado	18.92
Upper Gila	32.43
Santa Cruz	16.22
San Pedro	21.62
Willcox Playa	43.24
San Simon	8.11
White Water Draw	43.24

AUGUST 2006 - OCTOBER 2007 (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	2.86	CD1	92.04
Upper Colorado	59.46	CD2	92.92
Little Colorado	51.35	CD3	95.58
Verde	56.76	CD4	97.35
Bill Williams	56.76	CD5	93.81
Agua Fria	32.43	CD6	97.35
Lower Gila	78.38	CD7	95.58
Salt	51.35
Lower Colorado	59.46
Upper Gila	43.24
Santa Cruz	37.84
San Pedro	37.84
Willcox Playa	48.65
San Simon	32.43
White Water Draw	47.22

MAY 2006 – OCTOBER 2007 (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 in most of the state. Three watersheds in the southern part of the state were between the 8^th and 14^th percentile, and the other 12 watersheds were all below the 23^rd percentile, putting this year on the dry side of the drought tally. The entire state continued to have temperatures above the 85^th percentile during the previous 12 months. Many locations had daily records tied or broken for both maximum and minimum temperatures.

The two year period continues to show the driest conditions of all periods. The last wet year was 2005, with high precipitation totals for both winter and summer in most places. Since then, we have had two very dry years, punctuated with an occasional wet month, usually in summer. The Virgin, Bill Williams, Agua Fria, Salt, Santa Cruz, and San Simon watersheds are all below the 9^th percentile for the 24-month period. Exceptions are WIllcox Playa and White Water Draw in the southeast, which have benefited from two moderately wet monsoons, bringing them above the 42^nd percentile. Temperatures continue to be above the 81^st percentile, with the southern and southeastern counties have the hottest conditions.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	2.94	CD1	87.50
Upper Colorado	22.22	CD2	91.07
Little Colorado	16.67	CD3	93.75
Verde	11.11	CD4	94.64
Bill Williams	11.11	CD5	88.39
Agua Fria	5.56	CD6	94.64
Lower Gila	33.33	CD7	95.54
Salt	5.56
Lower Colorado	19.44
Upper Gila	13.89
Santa Cruz	8.33
San Pedro	11.11
Willcox Playa	28.57
San Simon	8.33
White Water Draw	38.89

NOVEMBER 2006 – OCTOBER 2007 (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	3.12	CD1	81.08
Upper Colorado	11.43	CD2	92.79
Little Colorado	17.14	CD3	91.89
Verde	11.43	CD4	93.69
Bill Williams	2.86	CD5	91.89
Agua Fria	5.71	CD6	96.40
Lower Gila	11.43	CD7	100.00
Salt	8.57
Lower Colorado	17.14
Upper Gila	17.14
Santa Cruz	5.71
San Pedro	22.86
Willcox Playa	45.71
San Simon	5.71
White Water Draw	42.86

NOVEMBER 2005 – OCTOBER 2007 (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 precipitation period continues to show the results of the wet winter of 2004-05 in northern and western Arizona. The central and eastern watersheds are near average, and the southern watersheds are well below-average, now below the 9^th percentile. The two more recent dry years are gradually bringing the 36-month percentiles down. Temperatures over the 3-year period range from the 77^th percentile to the 100^th percentile in the southeast. This pattern has not changed in nearly a year, showing that even the monsoon, which generally lowers temperatures for two months due to cloudiness and cooling, does not have much impact on a 36 month record.

The 48-month period precipitation is also above average across the northern part of the state, and well below average in south central Arizona. Three watersheds are above the 66^th percentile, mostly in the north; three more are near normal, averaging at the 48^th percentile; five are below the 25^th percentile; and 2 are below the 13^th percentile. The warm conditions continue with two of the southern climate divisions above the 96^th percentile for temperature, and the southeast climate division at the 100^th percentile again.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	62.50	CD1	77.27
Upper Colorado	58.82	CD2	91.82
Little Colorado	35.29	CD3	90.00
Verde	44.12	CD4	94.55
Bill Williams	32.35	CD5	88.18
Agua Fria	38.24	CD6	98.18
Lower Gila	52.94	CD7	100.00
Salt	35.29
Lower Colorado	64.71
Upper Gila	29.41
Santa Cruz	8.82
San Pedro	29.41
Willcox Playa	38.24
San Simon	8.82
White Water Draw	47.06

NOVEMBER 2004 – OCTOBER 2007 (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	70.00	CD1	77.06
Upper Colorado	66.67	CD2	90.83
Little Colorado	27.27	CD3	90.83
Verde	48.48	CD4	95.41
Bill Williams	33.33	CD5	88.07
Agua Fria	21.21	CD6	94.50
Lower Gila	45.45	CD7	100.00
Salt	24.24
Lower Colorado	69.70
Upper Gila	33.33
Santa Cruz	6.06
San Pedro	21.21
Willcox Playa	39.39
San Simon	12.12
White Water Draw	51.52

NOVEMBER 2003 – OCTOBER 2007 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

November 2007 Arizona Drought Update based on Precipitation (data through October 2007)

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 was extremely dry, with all watersheds, except the lower Colorado, below the 22^nd percentile. The lower Colorado typically receives almost no rainfall in October, so their percentile was almost average. For the second month in a row, temperatures were somewhat cooler than previous months. The northern counties were below the 70^th percentile and the warmest, in the southeast, were between the 76^th and 85^th percentile. The lack of fall rainfall will impact the spring run-off, as dry soil tends to absorb the snowmelt, reducing the flow into the reservoirs.

The 3-month period of August through October, was near average on the upper Colorado, but below average everywhere else, because the tail end of the monsoon was fairly dry, and the fall has been dry as well. The clear skies and dry weather have pushed the temperatures above the 81^st percentile everywhere in the state. Maricopa and Pinal counties were the warmest and Yavapai County was the coolest.

The 6-month period rainfall was near average for much of the state, and below average in the south central watersheds. The lower Gila had slightly above average rainfall in the past 6 months, due to heavy July precipitation in Gila Bend, Laveen, and Wickenburg. Temperatures in the northern and western part of the state were around the 93^rd percentile, and in the southeastern part of the state the temperatures were between the 95^th and 98^th percentile. Some early frontal systems brought cooler weather to the higher elevations, and the first freezing temperature was reported in September, and nighttime temperatures have dropped below freezing regularly at the higher elevations.

The 12-month period has been extremely dry in most of the state. Three watersheds in the southern part of the state were between the 8^th and 14^th percentile, and the other 12 watersheds were all below the 23^rd percentile, putting this year on the dry side of the drought tally. The entire state continued to have temperatures above the 85^th percentile during the previous 12 months. Many locations had daily records tied or broken for both maximum and minimum temperatures.

The two year period continues to show the driest conditions of all periods. The last wet year was 2005, with high precipitation totals for both winter and summer in most places. Since then, we have had two very dry years, punctuated with an occasional wet month, usually in summer. The Virgin, Bill Williams, Agua Fria, Salt, Santa Cruz, and San Simon watersheds are all below the 9^th percentile for the 24-month period. Exceptions are WIllcox Playa and White Water Draw in the southeast, which have benefited from two moderately wet monsoons, bringing them above the 42^nd percentile. Temperatures continue to be above the 81^st percentile, with the southern and southeastern counties have the hottest conditions.

The 36-month precipitation period continues to show the results of the wet winter of 2004-05 in northern and western Arizona. The central and eastern watersheds are near average, and the southern watersheds are well below-average, now below the 9^th percentile. The two more recent dry years are gradually bringing the 36-month percentiles down. Temperatures over the 3-year period range from the 77^th percentile to the 100^th percentile in the southeast. This pattern has not changed in nearly a year, showing that even the monsoon, which generally lowers temperatures for two months due to cloudiness and cooling, does not have much impact on a 36 month record.

The 48-month period precipitation is also above average across the northern part of the state, and well below average in south central Arizona. Three watersheds are above the 66^th percentile, mostly in the north; three more are near normal, averaging at the 48^th percentile; five are below the 25^th percentile; and 2 are below the 13^th percentile. The warm conditions continue with two of the southern climate divisions above the 96^th percentile for temperature, and the southeast climate division at the 100^th percentile again.