State Precipitation & Temperature Update for Arizona

Conditions through September 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 10/21/2007. The data are preliminary, and there are no data for the Virgin River watershed.

Precipitation Percentiles by Watershed (through September 2007)

Temperature Percentiles by Climate Division (through September 2007)

SHORT TERM CONDITIONS: 1-6 MONTHS

September can be either wet or dry, depending on when the monsoon ends, and whether moisture from eastern Pacific hurricanes is drawn into the state. This year’s monsoon brought average to above average precipitation to all watersheds except those in the southeast. The Salt and Verde watersheds received above average precipitation, while the Upper Gila had well below average precipitation, and the San Pedro, Whitewater Draw and Willcox Play had slightly below average precipitation. All the other watersheds have average precipitation. Temperatures were somewhat cooler in September then in previous months. Yavapai, Yuma and La Paz counties were below the 70% percentile and the hottest climate divisions, including the Colorado Plateau and Maricopa and Pinal counties were between the 90^th and 93^rd percentiles. The 3-month period, covering the monsoon, brought above average precipitation to most of the state. The southeast had near average precipitation, while the northern watersheds were above the 83^rd percentile. The wet monsoon kept temperatures from rising too far above average. The entire state was above the 90^th percentile, and Maricopa, Pinal and Gila counties were above the 97th percentile. The 6-month period had above average rainfall in the north, along the lower Colorado River in the west, in the eastern mountains, and in the southwest. The Bill Williams, Agua Fria and southern watersheds had average rainfall for the 6-month period. The spring and summer temperatures have been above the 90^th percentile everywhere in the state, and above the 95^th percentile in the central and northwestern climate divisions.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	-99	CD1	90.27
Upper Colorado	54.05	CD2	84.07
Little Colorado	43.24	CD3	69.91
Verde	62.16	CD4	82.30
Bill Williams	45.95	CD5	63.72
Agua Fria	40.54	CD6	92.04
Lower Gila	48.65	CD7	79.65
Salt	64.86
Lower Colorado	45.95
Upper Gila	24.32
Santa Cruz	40.54
San Pedro	35.14
Willcox Playa	35.14
San Simon	40.54
White Water Draw	37.84

SEPTEMBER 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	-99	CD1	94.69
Upper Colorado	83.78	CD2	94.69
Little Colorado	86.49	CD3	94.69
Verde	86.49	CD4	97.35
Bill Williams	70.27	CD5	92.04
Agua Fria	51.35	CD6	99.12
Lower Gila	86.49	CD7	90.27
Salt	67.57
Lower Colorado	70.27
Upper Gila	70.27
Santa Cruz	51.35
San Pedro	54.05
Willcox Playa	56.76
San Simon	54.05
White Water Draw	52.78

JULY 2006 - SEPTEMBER 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	-99	CD1	93.81
Upper Colorado	72.97	CD2	95.58
Little Colorado	67.57	CD3	96.46
Verde	64.86	CD4	96.46
Bill Williams	56.76	CD5	90.27
Agua Fria	40.54	CD6	97.35
Lower Gila	86.49	CD7	93.81
Salt	64.86
Lower Colorado	67.57
Upper Gila	64.86
Santa Cruz	45.95
San Pedro	43.24
Willcox Playa	56.76
San Simon	48.65
White Water Draw	55.56

APRIL 2006 – SEPTEMBER 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 had average precipitation in the upper Colorado, upper and lower Gila and Whitewater Draw watersheds. All others were below average, with the Agua Fria, San Simon and Santa Cruz the driest, below the 13^th percentile. The entire state had temperatures above the 85^th percentile during the previous 12 months.

The two year period continues to show the driest conditions of all periods. The Bill Williams and Agua Fria watersheds in central Arizona and the San Simon and Santa Cruz in south central Arizona are below the 5^th percentile for precipitation. The Salt and Verde watersheds in central Arizona are below the 12^th percentile, and four other watersheds are below the 23^rd percentile. The southeast and southwest watersheds are between the 25^th and 40^th percentiles. The Willcox Playa at the 48^th percentile is the closest to having average precipitation for the two year period, mostly due to two consecutive wet monsoon seasons. Temperatures in the state for the two-year period are well above average everywhere, with the northeast Colorado Plateau having the coolest temperatures at the 82^nd percentile. The southeast climate divisions continue to be above the 96^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	-99	CD1	85.71
Upper Colorado	50.00	CD2	87.05
Little Colorado	27.78	CD3	91.96
Verde	25.00	CD4	91.07
Bill Williams	19.44	CD5	86.61
Agua Fria	13.89	CD6	91.96
Lower Gila	41.67	CD7	94.64
Salt	27.78
Lower Colorado	33.33
Upper Gila	41.67
Santa Cruz	8.33
San Pedro	25.00
Willcox Playa	31.43
San Simon	11.11
White Water Draw	44.44

OCTOBER 2006 – SEPTEMBER 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	-99	CD1	82.88
Upper Colorado	17.14	CD2	92.79
Little Colorado	20.00	CD3	91.89
Verde	11.43	CD4	93.69
Bill Williams	2.86	CD5	90.99
Agua Fria	2.86	CD6	96.40
Lower Gila	20.00	CD7	100.00
Salt	8.57
Lower Colorado	25.71
Upper Gila	22.86
Santa Cruz	2.86
San Pedro	31.43
Willcox Playa	48.57
San Simon	2.86
White Water Draw	40.00

OCTOBER 2005 – SEPTEMBER 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 still shows 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, under the 12^th percentile. Temperatures over the 3-year period have been well above average, over the 75^th percentile for all climate divisions. The southern climate divisions continue to be above the 95^th percentile, as a result of record-breaking temperatures in 2005 and 2006.

The 48-month period precipitation is also above average across the northern part of the state, and well below average in south central Arizona. Nine of the fifteen watersheds are below the 40^th percentile, with the Santa Cruz below the 5^th percentile, and San Simon below the 10^th percentile. The warm conditions continue with three of the southern climate divisions above the 96^th percentile for temperature.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	-99	CD1	76.36
Upper Colorado	67.65	CD2	91.82
Little Colorado	41.18	CD3	90.00
Verde	52.94	CD4	94.55
Bill Williams	44.12	CD5	84.55
Agua Fria	47.06	CD6	95.45
Lower Gila	64.71	CD7	100.00
Salt	38.24
Lower Colorado	85.29
Upper Gila	50.00
Santa Cruz	11.76
San Pedro	26.47
Willcox Playa	41.18
San Simon	11.76
White Water Draw	50.00

OCTOBER 2004 – SEPTEMBER 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	-99	CD1	77.98
Upper Colorado	69.70	CD2	90.37
Little Colorado	27.27	CD3	93.58
Verde	45.45	CD4	96.33
Bill Williams	36.36	CD5	88.07
Agua Fria	21.21	CD6	98.17
Lower Gila	42.42	CD7	100.00
Salt	27.27
Lower Colorado	69.70
Upper Gila	36.36
Santa Cruz	3.03
San Pedro	27.27
Willcox Playa	39.39
San Simon	9.09
White Water Draw	51.52

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

October 2007 Arizona Drought Update based on Precipitation (data through September 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

The 3-month period, covering the monsoon, brought above average precipitation to most of the state. The southeast had near average precipitation, while the northern watersheds were above the 83^rd percentile. The wet monsoon kept temperatures from rising too far above average. The entire state was above the 90^th percentile, and Maricopa, Pinal and Gila counties were above the 97th percentile.

The 6-month period had above average rainfall in the north, along the lower Colorado River in the west, in the eastern mountains, and in the southwest. The Bill Williams, Agua Fria and southern watersheds had average rainfall for the 6-month period. The spring and summer temperatures have been above the 90^th percentile everywhere in the state, and above the 95^th percentile in the central and northwestern climate divisions.