State Precipitation & Temperature Update for Arizona

Conditions through May 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 4528/2007. The data are preliminary, and some data are missing from the San Pedro watershed.

Precipitation Percentiles by Watershed (through May 2007)

Temperature Percentiles by Climate Division (through May 2007)

SHORT TERM CONDITIONS: 1-6 MONTHS

May 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. Precipitation for the 3-month period of March through May 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 March and April. The lack of frontal storm systems also resulted in temperatures above the 88^th percentile everywhere in the state. 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.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	24.32	CD1	88.05
Upper Colorado	54.05	CD2	78.32
Little Colorado	56.76	CD3	89.38
Verde	32.43	CD4	96.46
Bill Williams	37.84	CD5	84.96
Agua Fria	43.24	CD6	91.15
Lower Gila	51.35	CD7	88.05
Salt	56.76
Lower Colorado	22.97
Upper Gila	67.57
Santa Cruz	37.84
San Pedro	40.54
Willcox Playa	70.27
San Simon	13.51
White Water Draw	59.46

MAY 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	16.22	CD1	93.81
Upper Colorado	27.03	CD2	92.92
Little Colorado	18.92	CD3	91.15
Verde	16.22	CD4	96.46
Bill Williams	10.81	CD5	88.50
Agua Fria	16.22	CD6	92.04
Lower Gila	45.95	CD7	92.04
Salt	18.92
Lower Colorado	44.59
Upper Gila	51.35
Santa Cruz	21.62
San Pedro	54.05
Willcox Playa	75.68
San Simon	37.84
White Water Draw	81.08

MARCH 2006 - MAY 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	17.14	CD1	84.07
Upper Colorado	22.22	CD2	75.22
Little Colorado	20.00	CD3	79.65
Verde	17.14	CD4	91.15
Bill Williams	11.11	CD5	76.11
Agua Fria	16.67	CD6	84.96
Lower Gila	19.44	CD7	72.57
Salt	25.00
Lower Colorado	16.67
Upper Gila	38.89
Santa Cruz	25.00
San Pedro	35.29
Willcox Playa	48.57
San Simon	19.44
White Water Draw	54.29

DECEMBER 2006 – MAY 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

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.

The 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.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	20.59	CD1	80.36
Upper Colorado	33.33	CD2	78.57
Little Colorado	30.56	CD3	86.61
Verde	19.44	CD4	87.50
Bill Williams	11.11	CD5	89.29
Agua Fria	25.00	CD6	88.39
Lower Gila	25.00	CD7	90.18
Salt	33.33
Lower Colorado	25.00
Upper Gila	58.33
Santa Cruz	41.67
San Pedro	69.44
Willcox Playa	74.29
San Simon	22.22
White Water Draw	68.57

JUNE 2006 – MAY 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	18.18	CD1	75.68
Upper Colorado	8.57	CD2	87.39
Little Colorado	8.57	CD3	89.64
Verde	5.71	CD4	92.79
Bill Williams	2.86	CD5	88.29
Agua Fria	2.86	CD6	94.59
Lower Gila	8.57	CD7	100.00
Salt	5.71
Lower Colorado	28.57
Upper Gila	20.00
Santa Cruz	8.57
San Pedro	28.57
Willcox Playa	40.00
San Simon	5.71
White Water Draw	34.29

JUNE 2005 – MAY 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 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.

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.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	81.25	CD1	74.55
Upper Colorado	61.76	CD2	89.09
Little Colorado	29.41	CD3	88.18
Verde	44.12	CD4	95.45
Bill Williams	41.18	CD5	89.09
Agua Fria	32.35	CD6	90.91
Lower Gila	47.06	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

JUNE 2004 – MAY 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	-99.99	CD1	77.98
Upper Colorado	51.52	CD2	89.91
Little Colorado	24.24	CD3	93.58
Verde	30.30	CD4	96.33
Bill Williams	30.30	CD5	89.91
Agua Fria	21.21	CD6	97.25
Lower Gila	39.39	CD7	100.00
Salt	27.27
Lower Colorado	66.67
Upper Gila	24.24
Santa Cruz	12.12