State Precipitation & Temperature Update for Arizona

Conditions through June 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 7/25/2007. The data are preliminary.

Precipitation Percentiles by Watershed (through June 2007)

Temperature Percentiles by Climate Division (through June 2007)

SHORT TERM CONDITIONS: 1-6 MONTHS

June is generally a dry month across Arizona, and this year was no exception for most of the state, except the southeast corner which received above-average rainfall due to moisture moving southwest from New Mexico. New Mexico has had a very rainy month. Temperatures across the state were well above average, with Gila county temperatures in the 95^th percentile. For the 3-month period of April through June, precipitation was well below average, as there was little moisture for the spring frontal systems to work on. The dry conditions contributed to higher temperatures during the three month period with all climate divisions above the 79^th percentile. The 6-month precipitation map reflects the dry winter and spring with only the southeastern watersheds above the 28th percentile. Temperatures were below the 85^th percentile in the north and west, and above the 88^th percentile in the central and southeastern climate divisions.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	13.89	CD1	83.19
Upper Colorado	2.70	CD2	86.73
Little Colorado	37.84	CD3	86.28
Verde	13.51	CD4	95.58
Bill Williams	17.57	CD5	69.91
Agua Fria	18.92	CD6	88.05
Lower Gila	48.65	CD7	89.38
Salt	35.14
Lower Colorado	29.73
Upper Gila	72.97
Santa Cruz	24.32
San Pedro	81.08
Willcox Playa	60.81
San Simon	51.35
White Water Draw	67.57

JUNE 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	22.22	CD1	86.28
Upper Colorado	32.43	CD2	88.50
Little Colorado	21.62	CD3	92.04
Verde	8.11	CD4	98.23
Bill Williams	10.81	CD5	79.65
Agua Fria	13.51	CD6	86.73
Lower Gila	35.14	CD7	87.17
Salt	24.32
Lower Colorado	32.43
Upper Gila	51.35
Santa Cruz	21.62
San Pedro	40.54
Willcox Playa	59.46
San Simon	29.73
White Water Draw	59.46

APRIL 2006 - JUNE 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	14.29	CD1	84.07
Upper Colorado	18.92	CD2	84.07
Little Colorado	22.22	CD3	88.50
Verde	16.22	CD4	93.81
Bill Williams	8.11	CD5	78.76
Agua Fria	18.92	CD6	89.38
Lower Gila	27.03	CD7	91.15
Salt	21.62
Lower Colorado	18.92
Upper Gila	45.95
Santa Cruz	18.92
San Pedro	43.24
Willcox Playa	52.78
San Simon	18.92
White Water Draw	66.67

JANUARY 2006 – JUNE 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 both the past winter and last year’s monsoon. For all areas of the state except the southeast, the entire 12 month period was exceptionally dry. The southeast watersheds received above-average rainfall during the 2006 monsoon season, bringing flooding to many locations, including Tucson. The extreme dryness is reflected in the higher than average temperatures. Temperatures are above the 79^th percentile everywhere in the state.

The two-year period precipitation is evidence of our two consecutive years of extreme dryness. The only watersheds above the 29^th percentile are Willcox Playa and White Water Draw, which received much needed rainfall during the 2006 monsoon. The entire state was very warm during the past 24 months, with the southeast and south central climate divisions having average temperatures above the 96^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	17.65	CD1	79.46
Upper Colorado	30.56	CD2	79.46
Little Colorado	27.78	CD3	82.14
Verde	13.89	CD4	85.27
Bill Williams	8.33	CD5	83.48
Agua Fria	22.22	CD6	87.50
Lower Gila	22.22	CD7	86.61
Salt	27.78
Lower Colorado	25.00
Upper Gila	58.33
Santa Cruz	36.11
San Pedro	66.67
Willcox Playa	80.00
San Simon	19.44
White Water Draw	71.43

JULY 2006 – JUNE 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	21.21	CD1	76.58
Upper Colorado	5.71	CD2	90.99
Little Colorado	11.43	CD3	90.09
Verde	2.86	CD4	91.89
Bill Williams	2.86	CD5	90.99
Agua Fria	2.86	CD6	96.40
Lower Gila	8.57	CD7	100.00
Salt	5.71
Lower Colorado	28.57
Upper Gila	17.14
Santa Cruz	8.57
San Pedro	25.71
Willcox Playa	42.86
San Simon	5.71
White Water Draw	45.71

JULY 2005 – JUNE 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 includes the wet winter of 2004-2005 for northern Arizona, and the dry monsoon for the southeast. The pattern is very different from the 24-month period, due to the wet 2004-2005 winter. Even though drought is occasionally punctuated by a wet year, the winter of 2004-2005 was not predicted, but was certainly welcome in many parts of the state. The 36-month^-temperature pattern has become hotter as all watersheds are now above the 74^th percentile, and six of the seven watersheds are above the 86th percentile.

The 48-month map shows that three of the past 4 years have been extremely dry throughout most of Arizona, with only the Virgin and Lower Colorado River watersheds above the 51^st percentile. Most of the eastern watersheds are below the 24^th percentile. Again, the 4-year dry period is accompanied by temperatures well above average across the state, with the southeast climate divisions above the 96^th percentile. The combination of high temperatures and dry conditions increases the evaporative demand for moisture, drying out the soil and stressing the vegetation.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	81.25	CD1	74.55
Upper Colorado	61.76	CD2	88.18
Little Colorado	32.35	CD3	88.18
Verde	47.06	CD4	94.55
Bill Williams	41.18	CD5	86.36
Agua Fria	32.35	CD6	93.64
Lower Gila	50.00	CD7	99.09
Salt	38.24
Lower Colorado	73.53
Upper Gila	38.24
Santa Cruz	5.88
San Pedro	23.53
Willcox Playa	38.24
San Simon	8.82
White Water Draw	47.06

JULY 2004 – JUNE 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	77.06
Upper Colorado	51.52	CD2	91.74
Little Colorado	21.21	CD3	94.50
Verde	27.27	CD4	96.33
Bill Williams	30.30	CD5	89.91
Agua Fria	21.21	CD6	98.17
Lower Gila	42.42	CD7	100.00
Salt	24.24
Lower Colorado	66.67
Upper Gila	24.24
Santa Cruz	12.12
San Pedro	18.18
Willcox Playa	21.21
San Simon	21.21
White Water Draw	36.36

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

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

June is generally a dry month across Arizona, and this year was no exception for all but the Upper Gila and San Pedro watersheds. Most of the state had less than average precipitation. Temperatures across the state were above average, but not as far above average as in the past two months. Maximum temperatures have not been much above normal, but frequent cloudy conditions have kept minimum temperatures above average.

Three-month period – Precipitation for the 3-month period of April through June was well below the 40^th percentile for the northern half of the state because the shift to La Niña conditions resulted in relatively dry conditions in April and May. The lack of frontal storm systems also resulted in temperatures above the 88^th percentile everywhere in the state.

Six-month period – The 6-month precipitation map still shows the effects of the dry winter with only four watersheds in the southeast corner of the state above the 25^th percentile. Temperatures were above average everywhere in the state for the 6-month period.

Twelve-month period – All watersheds except those in the southeast are well below average for the 12 month period. The San Pedro, Willcox Playa, and White Water Draw watersheds in the southeast have had above average precipitation both during the 2006 summer, and the 2007 winter. Temperatures are above the 78^th percentile everywhere in the state.

Two-year period - has consistently been the driest period with all watersheds receiving well below average precipitation, nine are below the 9^th percentile and two are below the 3^rd percentile. This indicates that the drought is experiencing a cyclic wet-dry regime where each phase seems to last 12 months. For temperature, again all divisions are above the 75^th percentile, exacerbating the dry conditions. The southeast climate division continues to be at the 100^th percentile.

Three-year period - The 36-month precipitation is well below average in the southeastern watersheds and above average for the northern and western watersheds. This period includes the wet winter of 2005. The 36-month^-temperature pattern has been consistent for the past five updates, with Gila County and the southeast climate division still above the 95^th percentile for temperature, and all others above the 77^th percentile.

Four-year period - All watersheds except the upper and lower Colorado have had well below average precipitation in the 48 month period. The three south central – southeast climate divisions remain above the 95^th percentile for temperature, due to the three warm dry winters of 2004-2006, in this region.