State Precipitation & Temperature Update for Arizona

Conditions through June 2008

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 07/21/2008. The data are preliminary.

Precipitation Percentiles by Watershed (through June 2008)

Temperature Percentiles by Climate Division (through June 2008)

SHORT TERM CONDITIONS: 1-6 MONTHS

June is normally dry statewide, unless the monsoon activity begins early. This year the rainfall began early in southern Arizona, with the lower Gila, Santa Cruz and San Simon watersheds all above the 80^th percentile. The Aga Fria and Salt River watersheds were near average, but the rest of the watersheds were below average, between the 18^th and 40^th percentiles. Temperatures were up significantly since last month, with the northern half of the state between the 77^th and 85^th percentiles, and the southern half of the state between the 92^nd and 94^th percentiles. The three-month period of April through June was drier than average in the northern half of the state, and near- or above-average in the southern half of the state. The notable dry exceptions in the southeast are the Willcox and Whitewater Draw watersheds, which remain below the 30^th percentile. There is definite short-term improvement, as last month the three month interval was the driest of all the intervals, with 8 watersheds below the 15^th percentile, and 12 watersheds below the 25^th percentile. The three-month temperatures continue to be near- or slightly above-average. The six-month period precipitation, from January through June, was near average in the central watersheds, above average in the Salt and Upper Colorado watersheds, and below average in the southeast, with the Willcox Playa and Whitewater Draw still below the 18^th percentile. Temperatures were near average in the northeast and Yavapai County, slightly above average along the lower Colorado River, and well above average in the southeast.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	45.95	CD1	84.65
Upper Colorado	36.84	CD2	79.82
Little Colorado	36.84	CD3	82.89
Verde	34.21	CD4	77.63
Bill Williams	18.42	CD5	92.98
Agua Fria	42.11	CD6	93.86
Lower Gila	92.11	CD7	92.11
Salt	55.26
Lower Colorado	30.26
Upper Gila	26.32
Santa Cruz	86.84
San Pedro	65.79
Willcox Playa	23.68
San Simon	84.21
White Water Draw	26.32

JUNE 2008: 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	8.11	CD1	73.45
Upper Colorado	26.32	CD2	52.63
Little Colorado	36.84	CD3	57.46
Verde	23.68	CD4	71.05
Bill Williams	28.95	CD5	73.68
Agua Fria	28.95	CD6	70.18
Lower Gila	81.58	CD7	70.61
Salt	63.16
Lower Colorado	84.21
Upper Gila	47.37
Santa Cruz	47.37
San Pedro	52.63
Willcox Playa	28.95
San Simon	47.37
White Water Draw	28.95

APRIL 2008 - JUNE 2008 (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	16.67	CD1	66.37
Upper Colorado	68.42	CD2	44.74
Little Colorado	51.35	CD3	57.89
Verde	44.74	CD4	67.54
Bill Williams	52.63	CD5	70.18
Agua Fria	44.74	CD6	69.30
Lower Gila	57.89	CD7	79.82
Salt	65.79
Lower Colorado	52.63
Upper Gila	31.58
Santa Cruz	28.95
San Pedro	26.32
Willcox Playa	17.57
San Simon	44.74
White Water Draw	8.11

JANUARY 2008 – JUNE 2008 (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 above-average precipitation in five watersheds in the northeast and southwest parts of the state, near-average precipitation in six watersheds in central and southern Arizona, and below average precipitation in four watersheds in the southeast and northwest corners of the state. Temperatures were above the 73^rd percentile everywhere, with the warmest temperatures in the south and southeast climate divisions.

The 24-month period has seven watersheds near average for precipitation in the eastern half of the state, with two watersheds, the lower Gila and Willcox Playa, above average. Six watersheds are below average, with three between the 30th and 39^th percentiles, and 3 below the 22^nd percentile, all in the western half of Arizona. The 24-month interval shows much improvement as the dry months of 2006 are replaced by the wetter months of 2008. Temperatures for the 24-month are all below the 95^th percentile, but are all above the 73^rd percentile. The coolest areas are the northern climate divisions.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	5.71	CD1	73.45
Upper Colorado	75.68	CD2	75.22
Little Colorado	70.27	CD3	77.88
Verde	64.86	CD4	86.28
Bill Williams	45.95	CD5	79.65
Agua Fria	51.35	CD6	87.61
Lower Gila	72.97	CD7	92.04
Salt	72.97
Lower Colorado	59.46
Upper Gila	43.24
Santa Cruz	40.54
San Pedro	32.43
Willcox Playa	27.78
San Simon	54.05
White Water Draw	27.78

JULY 2008 – JUNE 2008 (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	2.94	CD1	73.21
Upper Colorado	47.22	CD2	78.57
Little Colorado	58.33	CD3	85.71
Verde	30.56	CD4	85.71
Bill Williams	16.67	CD5	87.50
Agua Fria	22.22	CD6	89.29
Lower Gila	61.11	CD7	94.64
Salt	55.56
Lower Colorado	38.89
Upper Gila	52.78
Santa Cruz	41.67
San Pedro	52.78
Willcox Playa	61.11
San Simon	36.11
White Water Draw	58.33

JULY 2007 – JUNE 2008 (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 period continues to be the driest long-term period, with five central and southern watersheds below the 12^th percentile. Nine watersheds remain below the 25^th percentile, and all are below the 35^th percentile. For temperature, the two southeast climate divisions remain above the 95^th percentile while all the others are between the 76^th and 93^rd percentiles. Climate division 7 had the hottest 36-month period on record.

The 48-month period includes the wet winter of 2005 and is the wettest of the three long-term periods (24-, 36-, and 48-month). However, a comparison of the 36- and 48-month maps shows that the precipitation distribution was not uniform. Even though 2005 was wet in the northern watersheds, it was very dry in the southeast, as were the 36- and 12-month periods. Only four watersheds are above the 60^th percentile, while six watersheds are below the 40^th percentile for the long-term. Again all climate divisions are above the 75^th percentile for temperature, and the southeastern climate division is the hottest, but not quite the hottest on record. It is not a coincidence that the hottest climate divisions match up with the driest watersheds, and the coolest area match up with the wettest watersheds. The presence of cold fronts and cloudy conditions associated with precipitation tend to hold temperatures down. Unfortunately when temperatures climb due to clear skies and the absence of frontal systems, the higher temperatures increase the demand for soil moisture in evaporation and plant transpiration, worsening the impacts of drought on rangeland vegetation.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	9.09	CD1	76.58
Upper Colorado	31.43	CD2	88.29
Little Colorado	28.57	CD3	90.09
Verde	11.43	CD4	92.79
Bill Williams	5.71	CD5	87.39
Agua Fria	5.71	CD6	95.50
Lower Gila	28.57	CD7	100.00
Salt	20.00
Lower Colorado	34.29
Upper Gila	17.14
Santa Cruz	11.43
San Pedro	20.00
Willcox Playa	28.57
San Simon	8.57
White Water Draw	34.29

JULY 2006 – JUNE 2008 (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	43.75	CD1	75.45
Upper Colorado	67.65	CD2	90.00
Little Colorado	41.18	CD3	86.36
Verde	61.76	CD4	94.55
Bill Williams	47.06	CD5	84.55
Agua Fria	41.18	CD6	90.00
Lower Gila	64.71	CD7	99.09
Salt	44.12
Lower Colorado	76.47
Upper Gila	35.29
Santa Cruz	11.76
San Pedro	11.76
Willcox Playa	35.29
San Simon	20.59
White Water Draw	38.24

JULY 2005 – JUNE 2008 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

July 2008 Arizona Drought Update (based on precipitation data through June 2008)

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 of April through June was drier than average in the northern half of the state, and near- or above-average in the southern half of the state. The notable dry exceptions in the southeast are the Willcox and Whitewater Draw watersheds, which remain below the 30^th percentile. There is definite short-term improvement, as last month the three month interval was the driest of all the intervals, with 8 watersheds below the 15^th percentile, and 12 watersheds below the 25^th percentile. The three-month temperatures continue to be near- or slightly above-average.

The 6-month period precipitation, from January through June, was near average in the central watersheds, above average in the Salt and Upper Colorado watersheds, and below average in the southeast, with the Willcox Playa and Whitewater Draw still below the 18^th percentile. Temperatures were near average in the northeast and Yavapai County, slightly above average along the lower Colorado River, and well above average in the southeast.

The 24-month period has seven watersheds near average for precipitation in the eastern half of the state, with two watersheds, the lower Gila and Willcox Playa, above average. Six watersheds are below average, with three between the 30^th and 39^th percentiles, and three below the 22^nd percentile, all in the western half of Arizona. The 24-month interval shows much improvement as the dry months of 2006 are replaced by the wetter months of 2008. Temperatures for the 24-month period are all below the 95^th percentile, but are all above the 73^rd percentile. The coolest areas are the northern climate divisions.