State Precipitation & Temperature Update for Arizona

Conditions through July 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 8/25/2007. The data are preliminary.

Precipitation Percentiles by Watershed (through July 2007)

Temperature Percentiles by Climate Division (through July 2007)

SHORT TERM CONDITIONS: 1-6 MONTHS

July is generally a wet month across Arizona, and this year was no exception for most of the state, except the northwest corner, which received slightly below-average rainfall. The monsoon, so far, has been extremely wet across most of the state. The southeast, which normally has the wettest summer has been slightly below the central and eastern mountain basins. Temperatures across the state were well above average, with only the lower Colorado River division below the 95^th percentile. For the 3-month period of May through July, precipitation was also well above average, for most of the state. Only the Virgin River basin and the southeast watersheds were near or below their May-July averages. The wet conditions helped to decrease temperatures below the 95^th percentile, where they had been through the drier months. The 6-month period spans the dry winter from February through the wet summer month of July, with most watersheds either slightly above or slightly below average precipitation. Temperatures were above the 85^th percentile everywhere in the state, and above the 95th^th percentile in the central and northeastern climate divisions.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	38.89	CD1	97.35
Upper Colorado	91.89	CD2	98.23
Little Colorado	89.19	CD3	99.12
Verde	91.89	CD4	99.12
Bill Williams	81.08	CD5	92.04
Agua Fria	91.89	CD6	99.12
Lower Gila	97.30	CD7	96.46
Salt	94.59
Lower Colorado	94.59
Upper Gila	72.97
Santa Cruz	75.68
San Pedro	67.57
Willcox Playa	62.16
San Simon	91.89
White Water Draw	55.56

JULY 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	5.56	CD1	93.81
Upper Colorado	86.49	CD2	94.69
Little Colorado	81.08	CD3	93.81
Verde	81.08	CD4	98.23
Bill Williams	64.86	CD5	89.38
Agua Fria	81.08	CD6	94.69
Lower Gila	97.30	CD7	94.69
Salt	78.38
Lower Colorado	94.59
Upper Gila	67.57
Santa Cruz	70.27
San Pedro	54.05
Willcox Playa	56.76
San Simon	91.89
White Water Draw	55.56

MAY 2006 - JULY 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	11.11	CD1	92.92
Upper Colorado	43.24	CD2	96.46
Little Colorado	37.84	CD3	96.46
Verde	27.03	CD4	94.69
Bill Williams	18.92	CD5	92.04
Agua Fria	35.14	CD6	95.58
Lower Gila	70.27	CD7	94.69
Salt	29.73
Lower Colorado	64.86
Upper Gila	45.95
Santa Cruz	37.84
San Pedro	40.54
Willcox Playa	52.78
San Simon	56.76
White Water Draw	58.33

FEBRUARY 2006 – JULY 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 reflects winter of 2006-07 and the end of the 2006 monsoon season. For all watersheds in the state except White Water Draw and Willcox Playa in the southeast, the 12 month period was very dry. The Upper Gila had average precipitation at the 50^th percentile, and the rest of the state was below that, with three watersheds below the 26^th percentile. The twelve month period was relatively cooler than the other periods with no climate division above the 92^nd percentile. However, with all climate divisions above the 79^th percentile, it was still much warmer than the average.

The two-year period precipitation continues to be well below-average for all watersheds except White Water Draw. The rest of the state is below the 46^th percentile and 11 watersheds are at or below the 20^th percentile. This period includes two dry winters, one normal monsoon in 2006 and a dry monsoon in 2005. The entire state was very warm during the past 24 months, with a north-south temperature gradient. The high temperatures have increased the evaporative demand for water, reducing the water available for recharge.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	12.12	CD1	81.25
Upper Colorado	44.44	CD2	79.91
Little Colorado	30.56	CD3	85.71
Verde	25.00	CD4	85.71
Bill Williams	5.56	CD5	82.14
Agua Fria	36.11	CD6	87.05
Lower Gila	44.44	CD7	91.07
Salt	33.33
Lower Colorado	44.44
Upper Gila	50.00
Santa Cruz	27.78
San Pedro	47.22
Willcox Playa	60.00
San Simon	38.89
White Water Draw	66.67

AUGUST 2006 – JULY 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	18.18	CD1	78.38
Upper Colorado	14.29	CD2	90.09
Little Colorado	17.14	CD3	90.99
Verde	8.57	CD4	91.89
Bill Williams	5.71	CD5	90.09
Agua Fria	5.71	CD6	97.30
Lower Gila	11.43	CD7	100.00
Salt	8.57
Lower Colorado	34.29
Upper Gila	20.00
Santa Cruz	14.29
San Pedro	34.29
Willcox Playa	45.71
San Simon	5.71
White Water Draw	54.29

AUGUST 2005 – JULY 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 adds a wet winter to the two dry winters, and a second dry monsoon, resulting in a pattern of drier than average conditions in the southern half of the state, average precipitation in the central watersheds, and wetter than average conditions in the northern and western watersheds. The 36-month^-temperature pattern continues to show the southeast climate division as the hottest in 37 years and all but the northwestern climate division are above the 88^th percentile.

The 48-month map continues to show much drier than average conditions everywhere except the northernmost and westernmost watersheds. Six of the eastern and central watersheds are below the 25^th percentile. Temperatures in the southern climate divisions are above the 95^th percentile, and the northern and western climate divisions are above the 77^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	75.76	CD1	74.55
Upper Colorado	76.47	CD2	88.18
Little Colorado	41.18	CD3	88.18
Verde	52.94	CD4	94.55
Bill Williams	50.00	CD5	85.45
Agua Fria	41.18	CD6	94.55
Lower Gila	64.71	CD7	99.09
Salt	41.18
Lower Colorado	82.35
Upper Gila	38.24
Santa Cruz	8.82
San Pedro	17.65
Willcox Playa	41.18
San Simon	20.59
White Water Draw	47.06

AUGUST 2004 – JULY 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	64.52	CD1	77.98
Upper Colorado	66.67	CD2	89.91
Little Colorado	21.21	CD3	94.50
Verde	36.36	CD4	95.41
Bill Williams	39.39	CD5	88.07
Agua Fria	21.21	CD6	98.17
Lower Gila	51.52	CD7	100.00
Salt	27.27
Lower Colorado	75.76
Upper Gila	24.24
Santa Cruz	9.09
San Pedro	21.21
Willcox Playa	27.27
San Simon	24.24
White Water Draw	36.36

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

August 2007 Arizona Drought Update based on Precipitation (data through July 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

July is generally a wet month across Arizona, and this year was no exception for most of the state, except the northwest corner, which received slightly below-average rainfall. The monsoon, so far, has been extremely wet across most of the state. The southeast, which normally has the wettest summer has been slightly below the central and eastern mountain basins. Temperatures across the state were well above average, with only the lower Colorado River division below the 95^th percentile.

Three-month period – For the 3-month period of May through July, precipitation was also well above average, for most of the state. Only the Virgin River basin and the southeast watersheds were near or below their May-July averages. The wet conditions helped to decrease temperatures below the 95^th percentile, where they had been through the drier months.

Six-month period – spans the dry winter from February through the wet summer month of July, with most watersheds either slightly above or slightly below average precipitation. Temperatures were above the 85^th percentile everywhere in the state, and above the 95th^th percentile in the central and northeastern climate divisions.

Twelve-month period – reflects winter of 2006-07 and the end of the 2006 monsoon season. For all watersheds in the state except White Water Draw and Willcox Playa in the southeast, the 12 month period was very dry. The Upper Gila had average precipitation at the 50^th percentile, and the rest of the state was below that, with three watersheds below the 26^th percentile. The twelve month period was relatively cooler than the other periods with no climate division above the 92^nd percentile. However, with all climate divisions above the 79^th percentile, it was still much warmer than the average.

Two-year period - precipitation continues to be well below-average for all watersheds except White Water Draw. The rest of the state is below the 46^th percentile and 11 watersheds are at or below the 20^th percentile. This period includes two dry winters, one normal monsoon in 2006 and a dry monsoon in 2005. The entire state was very warm during the past 24 months, with a north-south temperature gradient. The high temperatures have increased the evaporative demand for water, reducing the water available for recharge.

Three-year period - The 36-month precipitation period adds a wet winter to the two dry winters, and a second dry monsoon, resulting in a pattern of drier than average conditions in the southern half of the state, average precipitation in the central watersheds, and wetter than average conditions in the northern and western watersheds. The 36-month^-temperature pattern continues to show the southeast climate division as the hottest in 37 years and all but the northwestern climate division are above the 88^th percentile.

Four-year period - The 48-month map continues to show much drier than average conditions everywhere except the northernmost and westernmost watersheds. Six of the eastern and central watersheds are below the 25^th percentile. Temperatures in the southern climate divisions are above the 95^th percentile, and the northern and western climate divisions are above the 77^th percentile.