State Precipitation & Temperature Update for Arizona

Conditions through July 2009

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 08/22/2009. Maps + Tables. The data are preliminary.

Precipitation Percentiles by Watershed (through July 2009)

Temperature Percentiles by Climate Division (through July 2009)

SHORT TERM CONDITIONS: 1-6 MONTHS

July precipitation was well above average in the lower Gila watershed, and near or below average in all other watersheds. The San Simon, White Water Draw and Virgin watersheds were the driest, at the 5^th, 4^th, and 7^th percentiles, respectively. The Bill Williams, Upper and Lower Colorado watersheds were near average. Temperature records were set statewide for July. The southern half of the state was above the 96^th percentile, while the northern half of the state was above the 90^th percentile. The three-month period of May through July was near average or wetter than average across most of Arizona, with the San Simon, White Water Draw and Virgin watersheds below average. The Upper Colorado and Lower Gila watersheds were above the 82^nd percentile. Temperatures for the three-month period were above the 83^rd percentile in all climate divisions. The six-month period is the worst of the short-term periods, with below average precipitation in all watersheds except the Willcox Playa. Nine watersheds had precipitation below the 24^th percentile, including five in southeastern Arizona and three in central Arizona. Temperatures over the last six months were between the 72^nd and 79^th percentile for central and northern Arizona, and at the 93^rd percentile in southern Arizona.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	6.58	CD1	90.43
Upper Colorado	41.03	CD2	93.91
Little Colorado	20.51	CD3	93.91
Verde	25.64	CD4	98.26
Bill Williams	58.97	CD5	98.26
Agua Fria	38.46	CD6	100.00
Lower Gila	76.92	CD7	96.52
Salt	30.77
Lower Colorado	48.72
Upper Gila	23.08
Santa Cruz	46.15
San Pedro	20.51
Willcox Playa	15.38
San Simon	5.13
White Water Draw	3.95

JULY 2009: 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	5.26	CD1	85.96
Upper Colorado	84.62	CD2	83.91
Little Colorado	64.10	CD3	87.83
Verde	51.28	CD4	90.43
Bill Williams	48.72	CD5	93.91
Agua Fria	51.28	CD6	97.39
Lower Gila	82.05	CD7	88.70
Salt	64.10
Lower Colorado	41.03
Upper Gila	51.28
Santa Cruz	41.03
San Pedro	56.41
Willcox Playa	64.10
San Simon	20.51
White Water Draw	34.21

MAY 2008 - JULY 2009 (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	2.63	CD1	72.81
Upper Colorado	25.64	CD2	75.22
Little Colorado	30.77	CD3	76.52
Verde	23.08	CD4	75.65
Bill Williams	20.51	CD5	78.26
Agua Fria	23.08	CD6	93.91
Lower Gila	38.46	CD7	93.04
Salt	25.64
Lower Colorado	33.33
Upper Gila	20.51
Santa Cruz	17.95
San Pedro	23.08
Willcox Playa	47.37
San Simon	12.82
White Water Draw	10.53

FEBRUARY 2008 – JULY 2009 (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 was near average in four watersheds and below average in eleven watersheds. The driest watersheds were in the southeast corner, plus the Little Colorado in the northeast. During the past 12 months, temperatures have been above the 78^th percentile in all areas of the state except Gila County, which was at the 67^th percentile.

The 24 month period is still the wettest long-term period; but only two watersheds, the Salt and lower Gila, had above average precipitation. Three watersheds were between the 40^th and 60^th percentiles, and ten watersheds were below the 38^th percentile. Temperatures were above the 82^nd percentile everywhere except the northwest corner of the state, in Mohave County, which was somewhat cooler, at the 71^st percentile. The warmest area is the Pinal-Maricopa County climate division, possibly due to the urban heat island influence of the Phoenix Metropolitan area.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	2.86	CD1	78.07
Upper Colorado	50.00	CD2	83.77
Little Colorado	21.05	CD3	85.96
Verde	31.58	CD4	67.54
Bill Williams	36.84	CD5	90.35
Agua Fria	28.95	CD6	98.25
Lower Gila	55.26	CD7	91.23
Salt	52.63
Lower Colorado	39.47
Upper Gila	42.11
Santa Cruz	13.16
San Pedro	21.05
Willcox Playa	16.22
San Simon	34.21
White Water Draw	18.42

AUGUST 2008 – JULY 2009 (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	2.86	CD1	70.80
Upper Colorado	56.76	CD2	82.30
Little Colorado	35.14	CD3	84.07
Verde	37.84	CD4	77.88
Bill Williams	32.43	CD5	89.38
Agua Fria	24.32	CD6	97.35
Lower Gila	72.97	CD7	90.27
Salt	72.97
Lower Colorado	32.43
Upper Gila	45.95
Santa Cruz	21.62
San Pedro	37.84
Willcox Playa	37.84
San Simon	40.54
White Water Draw	18.92

AUGUST 2007 – JULY 2009 (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 was drier than the 24-month period in all watersheds. Only the lower Gila received above average precipitation, at the 69^th percentile. Nine watersheds are at or below the 36^th percentile, and five watersheds had near average precipitation. Temperatures over the three-year period remain well above average, with only the northwest climate division below the 73^rd percentile, and the Pinal-Maricopa County division is the warmest at the 98^th percentile.

The 48-month period continues to be the driest long-term period, with only the lower Gila watershed near average at the 43^rd percentile. Fourteen watersheds are below the 35^th percentile, and six watersheds are below the 15^th percentile. The four-year temperatures continue to be the highest on record in the southern two climate divisions, and above the 89^th percentile in four other climate divisions. Only Mohave County is below the 76^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	2.86	CD1	72.32
Upper Colorado	41.67	CD2	83.04
Little Colorado	36.11	CD3	86.61
Verde	25.00	CD4	79.46
Bill Williams	16.67	CD5	88.84
Agua Fria	19.44	CD6	98.21
Lower Gila	69.44	CD7	91.07
Salt	55.56
Lower Colorado	36.11
Upper Gila	52.78
Santa Cruz	13.89
San Pedro	27.78
Willcox Playa	47.22
San Simon	30.56
White Water Draw	44.44

AUGUST 2006 – JULY 2009 (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	3.03	CD1	75.68
Upper Colorado	20.00	CD2	89.19
Little Colorado	17.14	CD3	89.19
Verde	14.29	CD4	90.09
Bill Williams	5.71	CD5	91.89
Agua Fria	2.86	CD6	100.00
Lower Gila	42.86	CD7	100.00
Salt	34.29
Lower Colorado	20.00
Upper Gila	25.71
Santa Cruz	8.57
San Pedro	22.86
Willcox Playa	34.29
San Simon	5.71
White Water Draw	28.57

AUGUST 2005 – JULY 2009 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

August 2009 Arizona Drought Update based on precipitation data through July 2009)

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 May through July was near average or wetter than average across most of Arizona, with the San Simon, White Water Draw and Virgin watersheds below average. The Upper Colorado and Lower Gila watersheds were above the 82^nd percentile. Temperatures for the three-month period were above the 83^rd percentile in all climate divisions.

The 6-month period is the worst of the short-term periods, with below average precipitation in all watersheds except the Willcox Playa. Nine watersheds had precipitation below the 24^th percentile, including five in southeastern Arizona and three in central Arizona. Temperatures over the last six months were between the 72^nd and 79^th percentile for central and northern Arizona, and at the 93^rd percentile in southern Arizona.