State Precipitation & Temperature Update for Arizona

Conditions through July 2006

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. Values of -99 and grey shading indicate missing data. When the data are available, this product will be updated. Current update is 08/25/2006.

Precipitation Percentiles by Watershed (through July 2006)

Temperature Percentiles by Climate Division (through July 2006)

SHORT TERM CONDITIONS: 1-6 MONTHS

The month of July was characterized by average or above average precipitation across the entire state, except the Bill Williams watershed in east central Arizona. The San Pedro watershed had the highest July precipitation in 36 years. It should be noted that the Willcox Playa only had 1 of 3 stations reporting for July. July was not quite as hot as June, but all climate divisions except CD1 in the north and CD7 in the southeast were above the 90% percentile. The Virgin and upper Colorado watersheds in the North, the Lower Gila in the Southwest and the White Water Draw in the Southeast had nearly normal precipitation for the 3 month period from May through July, while the eastern and central watersheds had above normal precipitation for the past 3 months. The Bill Williams and Agua Fria were the driest watersheds, but the lower Colorado was above the 80^th percentile. These high rainfall percentiles were accompanied by temperatures above the 95^th percentile across the southern and western climate division. Even the northwest and north central climate divisions had temperatures above the 85^th percentile for the 3 month period. The impact of the extremely dry winter is still apparent in the precipitation percentiles for the past 6-month period, with all watersheds except the San Pedro and Santa Cruz below the 50^th percentile. Those two were raised to the 83^rd and 61^st percentiles, respectively, as a result of the extremely wet July. The wetness of July provides significant drought relief that is apparent up through the 24 month period for the San Pedro watershed.. Temperatures for the 6-month period have been above the 75^th percentile everywhere across the state.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	55.71	CD1	85.71%
Upper Colorado	75.00	CD2	90.18%
Little Colorado	88.89	CD3	90.18%
Verde	75.00	CD4	93.75%
Bill Williams	38.89	CD5	95.54%
Agua Fria	58.33	CD6	91.96%
Lower Gila	50.00	CD7	78.57%
Salt	83.33
Lower Colorado	77.78
Upper Gila	77.78
Santa Cruz	91.67
San Pedro	100.00
Willcox Playa	63.89
San Simon	75.00
White Water Draw	57.14

JULY 2006: 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	54.29	CD1	91.96%
Upper Colorado	55.56	CD2	98.21%
Little Colorado	80.56	CD3	93.75%
Verde	72.22	CD4	95.54%
Bill Williams	38.89	CD5	98.21%
Agua Fria	38.89	CD6	98.21%
Lower Gila	58.33	CD7	96.43%
Salt	72.22
Lower Colorado	77.78
Upper Gila	66.67
Santa Cruz	91.67
San Pedro	100.00
Willcox Playa	58.33
San Simon	75.00
White Water Draw	57.14

MAY 2006 - JULY 2006 (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	48.57	CD1	79.46%
Upper Colorado	25.00	CD2	94.64%
Little Colorado	44.44	CD3	91.96%
Verde	38.89	CD4	93.75%
Bill Williams	11.11	CD5	88.39%
Agua Fria	16.67	CD6	94.64%
Lower Gila	36.11	CD7	92.86%
Salt	38.89
Lower Colorado	36.11
Upper Gila	27.78
Santa Cruz	61.11
San Pedro	83.33
Willcox Playa	22.86
San Simon	36.11
White Water Draw	20.00

FEBRUARY 2005 – JULY 2006 (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 intermediate time periods of 1- and 2-years show the importance of the historical context of drought. The 1-year period precipitation has been below the 15^th percentile for all watersheds except the Virgin, lower Colorado, San Pedro, and White Water Draw. The corresponding temperatures for the 1-year period have been extremely high, above the 85^th percentile everywhere except the northeast corner of the state, which is above the 75^th percentile.

In contrast, the 2-year period shows very little evidence of dryness across the western and west central portions of the state, with precipitation totals above normal. However, the Little Colorado and the southeastern watersheds show precipitation totals below the 35th percentile, with the driest watersheds being the San Pedro and Willcox Playa. This 2-year period still includes the extremely wet winter of 2005 with the extremely dry winter of 2006. Except for climate divisions 1 and 5 along the lower Colorado River, temperatures for the 2-year period were all at or above the 80^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	53.12	CD1	77.48%
Upper Colorado	11.43	CD2	90.99%
Little Colorado	14.29	CD3	90.09%
Verde	11.43	CD4	93.69%
Bill Williams	14.29	CD5	85.59%
Agua Fria	5.71	CD6	94.59%
Lower Gila	11.43	CD7	95.50%
Salt	8.57
Lower Colorado	31.43
Upper Gila	8.57
Santa Cruz	14.29
San Pedro	34.29
Willcox Playa	14.71
San Simon	5.71
White Water Draw	22.86

AUGUST 2005 – JULY 2006 (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	96.88	CD1	72.73%
Upper Colorado	85.29	CD2	88.18%
Little Colorado	38.24	CD3	86.36%
Verde	67.65	CD4	90.91%
Bill Williams	70.59	CD5	78.18%
Agua Fria	61.76	CD6	88.18%
Lower Gila	64.71	CD7	93.64%
Salt	47.06
Lower Colorado	91.18
Upper Gila	35.29
Santa Cruz	17.65
San Pedro	32.35
Willcox Playa	14.71
San Simon	26.47
White Water Draw	26.47

AUGUST 2004 – JULY 2006 (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 pattern of precipitation rankings for the longer-term 3-year period across the state is similar to that of the 2-year period, but includes another very dry winter from 2003-2004. Again, the western and northern watershed precipitation totals were at or above average, the central watersheds were at or slight below normal, and the southeastern watersheds were well below average. The entire state was above the 75^th percentile for temperature, and the 3-year period was among the warmest on record in CD 7 in the southeast areas of the state.

The length of the current drought and warming is more evident when looking at the longer 4-year period. The northern and western watersheds have had near or above normal precipitation during the 4-year period, while the eastern and southeastern watersheds have received precipitation well below the 25^th percentile. Along with the dryness has been excessive heat, particularly in the southeast. Climate divisions 3, 4, 6, and 7 in the south and south central areas have been above the 98^th percentile in the 4-year period, with division 7 still having the hottest 4-year period on record.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	90.62	CD1	77.06%
Upper Colorado	75.76	CD2	93.58%
Little Colorado	30.30	CD3	92.66%
Verde	54.55	CD4	96.33%
Bill Williams	63.64	CD5	88.99%
Agua Fria	36.36	CD6	95.41%
Lower Gila	60.61	CD7	99.08%
Salt	36.36
Lower Colorado	75.76
Upper Gila	18.18
Santa Cruz	12.12
San Pedro	21.21
Willcox Playa	12.12
San Simon	21.21
White Water Draw	27.27

AUGUST 2003 – JULY 2006 (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	-99.99	CD1	79.63%
Upper Colorado	65.62	CD2	90.74%
Little Colorado	18.75	CD3	96.30%
Verde	43.75	CD4	97.22%
Bill Williams	46.88	CD5	91.67%
Agua Fria	28.12	CD6	97.22%
Lower Gila	50.00	CD7	100.00%
Salt	25.00
Lower Colorado	75.00
Upper Gila	18.75
Santa Cruz	15.62
San Pedro	9.38
Willcox Playa	6.25
San Simon	21.88
White Water Draw	25.00

AUGUST 2002 – JULY 2006 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

August 2006 Arizona Drought Update based on Precipitation (data through July 2006)

The following summary describes the heat and dryness across the state for the 1-, 3-, 6-, 12-, 24-, 36-, and 48-month periods. This practice of categorizing the drought in terms of precipitation only will be discontinued as the long term impacts of drought in Arizona are also dependent on stream-flow, soil moisture and temperature, which are not considered here.

SUMMARY

● The arrival of the above average monsoon rainfall has brought relief from the recent dry conditions that have existed since March across most of the state. Although the 1 month rainfall does not end the drought, it improves the rangeland conditions and provides short term relief. The rainfall brought slightly cooler temperatures, although all areas of the state were above the 75^th percentile for temperature.

● Precipitation totals for the past 3- and 6-month periods were significantly improved by the wet July, particularly across the eastern and south central parts of the state. For the 6 month period, the north and northwest watersheds are still well blow average reflecting the dry spring in those watersheds. The warm winter and hot summer have had the greatest effect across the southern and western areas of the state.

● The dryness over the past 12 months is evident with almost all watersheds below the 15^th percentile for precipitation. The biggest change in the 12 month period is the San Pedro, which improved significantly with the wet July. The southeast has had temperatures above the 95^th percentile for the 12-month period.

● The west, north and central watersheds have had near or above average precipitation for the past 24 months, while the eastern and southeast watersheds have seen slightly to well below average precipitation in this period. Temperatures along the western border have been slightly above normal, but southeast and south central Arizona have had temperatures above the 85^th percentile.

● The 36-month precipitation totals are still at or above average for the 5 western watersheds in Arizona. Eastern central Arizona has had near or slightly below average precipitation for the 36-month period. The southeast has had precipitation totals well below normal, accompanied by temperatures among the highest on record.

● The long-term problematic areas within the state remain the east-central and southeastern regions, where 4-year precipitation totals are between the 15^th dan 5^th percentile. These dry conditions are exacerbated by temperatures above the 95^th percentile across the southeast, above the 85^th percentile in the southwest and northeast, and above the 75^th percentile in the northwest.