State Precipitation & Temperature Update for Arizona

Conditions through July 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 08/26/2008. The data are preliminary.

Precipitation Percentiles by Watershed (through July 2008)

Temperature Percentiles by Climate Division (through July 2008)

SHORT TERM CONDITIONS: 1-6 MONTHS

Although July is typically one of Arizona’s wettest months, due to the monsoon activity, this year was especially wet in all watersheds except the Virgin in northwestern Arizona. All watersheds, except the Virgin, were above the 63^rd percentile for July precipitation. The southern half of the state was above the 85^th percentile for precipitation. The San Pedro and Willcox watersheds had the wettest July since 1970. Temperatures in the southeastern counties were generally cooler than they have been in previous Julys, in the 32^nd percentile. The northeast was between the 66^th and 72^nd percentile, and the western third of the state was above the 75^th percentile. The monsoon activity also improved the three-month period of May through July, especially for the southern half of the state. The southern watersheds were all above the 86^th percentile, while the northern watersheds were between the 63^rd and 79^th percentiles. The Virgin was the dry watershed, below the 6^th percentile. Three-month temperatures were near or slightly above average in the eastern 2/3 of the state, and well above average along the lower Colorado River and in Maricopa and Pinal Counties. The six-month period precipitation, from February through July, was finally pushed above average in the southeastern watersheds and the lower Gila River watershed. The other southern and eastern watersheds were near average, and the northern and western watersheds remained below average, between the 23^rd and 40^th percentiles. The Virgin remained below the 10^th percentile for the six-month period. Temperatures for the six-month period were near or slightly above average in the northern half of the state and well above average in the southern half of the state.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	16.22	CD1	89.47
Upper Colorado	71.05	CD2	72.81
Little Colorado	73.68	CD3	75.88
Verde	63.16	CD4	66.67
Bill Williams	73.68	CD5	91.23
Agua Fria	76.32	CD6	90.35
Lower Gila	97.37	CD7	32.02
Salt	94.74
Lower Colorado	85.53
Upper Gila	97.37
Santa Cruz	89.47
San Pedro	100.00
Willcox Playa	100.00
San Simon	89.47
White Water Draw	97.30

JULY 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	5.41	CD1	77.43
Upper Colorado	63.16	CD2	60.96
Little Colorado	78.95	CD3	63.60
Verde	65.79	CD4	68.86
Bill Williams	71.05	CD5	88.60
Agua Fria	78.95	CD6	80.26
Lower Gila	97.37	CD7	57.02
Salt	97.37
Lower Colorado	92.11
Upper Gila	97.37
Santa Cruz	89.47
San Pedro	100.00
Willcox Playa	94.74
San Simon	92.11
White Water Draw	86.49

MAY 2008 - JULY 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	8.11	CD1	69.91
Upper Colorado	36.84	CD2	56.14
Little Colorado	42.11	CD3	64.91
Verde	23.68	CD4	64.91
Bill Williams	26.32	CD5	81.14
Agua Fria	26.32	CD6	76.75
Lower Gila	73.68	CD7	86.84
Salt	50.00
Lower Colorado	39.47
Upper Gila	65.79
Santa Cruz	57.89
San Pedro	84.21
Willcox Playa	72.97
San Simon	55.26
White Water Draw	64.86

FEBRUARY 2008 – JULY 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 precipitation is highly variable around the state, with near or above average precipitation in all watersheds except the Virgin and lower Colorado in the west. This is a significant improvement from last month, showing how important this very wet monsoon has been to the annual precipitation. The wet summer has brought relatively cooler temperatures to the northern half of the state, below the 75^th percentile. The southern half of the state remains above the 79^th percentile.

The 24-month period now has only four watersheds at or below the 25^th percentile, and they are scattered across the state from the north to the south. Three watersheds in the southern half of the state are above average, between the 66^th and 73^rd percentile. The other eight watersheds are near or slightly below average for the two-year period. Temperatures for the 24-month period are essentially unchanged from last month’s update, with all climate divisions above the 73^rd percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	5.88	CD1	72.12
Upper Colorado	70.27	CD2	69.03
Little Colorado	59.46	CD3	74.34
Verde	48.65	CD4	84.96
Bill Williams	43.24	CD5	79.65
Agua Fria	45.95	CD6	86.73
Lower Gila	75.68	CD7	92.92
Salt	72.97
Lower Colorado	37.84
Upper Gila	59.46
Santa Cruz	51.35
San Pedro	62.16
Willcox Playa	50.00
San Simon	56.76
White Water Draw	48.65

AUGUST 2008 – JULY 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	50.00	CD2	77.68
Little Colorado	44.44	CD3	84.82
Verde	30.56	CD4	83.04
Bill Williams	16.67	CD5	88.39
Agua Fria	25.00	CD6	87.05
Lower Gila	66.67	CD7	95.54
Salt	58.33
Lower Colorado	38.89
Upper Gila	58.33
Santa Cruz	25.00
San Pedro	50.00
Willcox Playa	72.22
San Simon	38.89
White Water Draw	66.67

AUGUST 2007 – JULY 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

Although the 36-month period remains the driest long-term period, with five central and southern watersheds below the 12^th percentile, four watersheds have moved above the 40^th percentile. Last month nine watersheds were below the 25^th percentile, and this month only six are below the 25^th percentile. Climate division 7 remains the hottest 36-month period on record, and the entire state is above the 76^th percentile for the 36-month temperature.

The 48-month period has only six watersheds below the 50^th percentile, while six are above the 50^th percentile, and three are above the 70^th percentile. The three driest watersheds are in the southeast, although this wet monsoon has improved their condition significantly. Temperatures for the four-year period remain extremely high, with climate division 7 in the southeast still the hottest 48-month period on record. All other climate divisions are above the 75^th percentile for temperature.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	8.82	CD1	76.58
Upper Colorado	28.57	CD2	87.39
Little Colorado	31.43	CD3	87.39
Verde	11.43	CD4	91.89
Bill Williams	5.71	CD5	89.19
Agua Fria	8.57	CD6	94.59
Lower Gila	45.71	CD7	100.00
Salt	25.71
Lower Colorado	31.43
Upper Gila	31.43
Santa Cruz	20.00
San Pedro	40.00
Willcox Playa	48.57
San Simon	8.57
White Water Draw	45.71

AUGUST 2006 – JULY 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	53.12	CD1	75.45
Upper Colorado	73.53	CD2	89.09
Little Colorado	44.12	CD3	87.27
Verde	55.88	CD4	94.55
Bill Williams	52.94	CD5	85.45
Agua Fria	44.12	CD6	92.73
Lower Gila	70.59	CD7	100.00
Salt	44.12
Lower Colorado	76.47
Upper Gila	50.00
Santa Cruz	17.65
San Pedro	26.47
Willcox Playa	50.00
San Simon	26.47
White Water Draw	50.00

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

August 2008 Arizona Drought Update (based on precipitation data through July 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

July: Although July is typically one of Arizona’s wettest months, due to the monsoon activity, this year was especially wet in all watersheds except the Virgin in northwestern Arizona. All watersheds, except the Virgin, were above the 63^rd percentile for July precipitation. The southern half of the state was above the 85^th percentile for precipitation. The San Pedro and Willcox watersheds had the wettest July since 1970. Temperatures in the southeastern counties were generally cooler than they have been in previous Julys, in the 32^nd percentile. The northeast was between the 66^th and 72^nd percentile, and the western third of the state was above the 75^th percentile.

The 3-month period: The monsoon activity also improved the three-month period of May through July, especially for the southern half of the state. The southern watersheds were all above the 86^th percentile, while the northern watersheds were between the 63^rd and 79^th percentiles. The Virgin was the dry watershed, below the 6^th percentile. Three-month temperatures were near or slightly above average in the eastern 2/3 of the state, and well above average along the lower Colorado River and in Maricopa and Pinal Counties.

The 6-month period precipitation, from February through July, was finally pushed above average in the southeastern watersheds and the lower Gila River watershed. The other southern and eastern watersheds were near average, and the northern and western watersheds remained below average, between the 23^rd and 40^th percentiles. The Virgin remained below the 10^th percentile for the six-month period. Temperatures for the six-month period were near or slightly above average in the northern half of the state and well above average in the southern half of the state.

The 12-month period precipitation is highly variable around the state, with near or above average precipitation in all watersheds except the Virgin and lower Colorado in the west. This is a significant improvement from last month, showing how important this very wet monsoon has been to the annual precipitation. The wet summer has brought relatively cooler temperatures to the northern half of the state, below the 75^th percentile. The southern half of the state remains above the 79^th percentile.

The 24-month period now has only four watersheds at or below the 25^th percentile, and they are scattered across the state from the north to the south. Three watersheds in the southern half of the state are above average, between the 66^th and 73^rd percentile. The other eight watersheds are near or slightly below average for the two-year period. Temperatures for the 24-month period are essentially unchanged from last month’s update, with all climate divisions above the 73^rd percentile.

The 36-month period: Although the 36-month period remains the driest long-term period, with five central and southern watersheds below the 12^th percentile, four watersheds have moved above the 40^th percentile. Last month nine watersheds were below the 25^th percentile, and this month only six are below the 25^th percentile. Climate division 7 remains the hottest 36-month period on record, and the entire state is above the 76^th percentile for the 36-month temperature.

The 48-month period has only six watersheds below the 50^th percentile, while six are above the 50^th percentile, and three are above the 70^th percentile. The three driest watersheds are in the southeast, although this wet monsoon has improved their condition significantly. Temperatures for the four-year period remain extremely high, with climate division 7 in the southeast still the hottest 48-month period on record. All other climate divisions are above the 75^th percentile for temperature.