State Precipitation & Temperature Update for Arizona

Conditions through April 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 05/14/2008. Upper Colorado watershed is missing 1 station. The data are preliminary.

Precipitation Percentiles by Watershed (through April 2008)

Temperature Percentiles by Climate Division (through April 2008)

SHORT TERM CONDITIONS: 1-6 MONTHS

April was extremely dry across the entire state. Precipitation was below the 10^th percentile for all watersheds except the lower Colorado, San Simon, and Santa Cruz. Even the wettest watershed was only at the 19^th percentile. Just as in March, only one winter storm moved through the state during April. And, for the second month in a row, temperatures were only slightly above average across most of the state. The three-month winter period of February through April was also drier than average across the state, as most places haven’t had precipitation since mid-February. The three month period saw temperatures slightly warmer than average across the entire state, significantly cooler than this period has been in previous years. The 6-month period precipitation, from November through April, was near- to slightly above-average in most watersheds, ranging from the 47^th to the 71^st percentile. The driest watershed was the Virgin, at the 36^th percentile. The storms tracked from the southwest to the northeast as they moved across the state, leaving the southeast and northwest corners of the state dry. Temperatures were near average on the Colorado Plateau, and slightly warmer in the central and western parts of the state. Gila and the southeastern counties were much warmer than average.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	5.26	CD1	67.54
Upper Colorado	7.89	CD2	48.25
Little Colorado	7.89	CD3	57.89
Verde	7.89	CD4	73.25
Bill Williams	6.58	CD5	60.09
Agua Fria	5.26	CD6	72.81
Lower Gila	9.21	CD7	67.54
Salt	7.89
Lower Colorado	19.74
Upper Gila	6.58
Santa Cruz	15.79
San Pedro	7.89
Willcox Playa	6.58
San Simon	10.53
White Water Draw	7.89

APRIL 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	21.05	CD1	67.11
Upper Colorado	31.58	CD2	52.63
Little Colorado	21.05	CD3	54.82
Verde	26.32	CD4	67.11
Bill Williams	21.05	CD5	68.86
Agua Fria	13.16	CD6	68.86
Lower Gila	13.16	CD7	65.35
Salt	15.79
Lower Colorado	18.42
Upper Gila	13.16
Santa Cruz	15.79
San Pedro	13.16
Willcox Playa	8.11
San Simon	21.05
White Water Draw	11.84

FEBRUARY 2008 - APRIL 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	35.71	CD1	61.40
Upper Colorado	70.27	CD2	57.02
Little Colorado	69.44	CD3	64.47
Verde	58.33	CD4	86.84
Bill Williams	54.05	CD5	71.05
Agua Fria	59.46	CD6	73.68
Lower Gila	70.27	CD7	81.14
Salt	67.57
Lower Colorado	48.65
Upper Gila	51.35
Santa Cruz	52.70
San Pedro	48.57
Willcox Playa	47.22
San Simon	72.97
White Water Draw	47.22

NOVEMBER 2008 – APRIL 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 near- to above-average precipitation in 11 watersheds, and below-average precipitation in the Virgin, Santa Cruz, San Pedro and Willcox watersheds. Temperatures were above the 75^th percentile for all climate divisions, with the highest temperatures in the south.

The 24-month period was much drier than it was last month, with no watersheds above the 59^th percentile. Three watersheds are still at or below the 25^th percentile, nine are between the 40^th and 59^th percentiles, while last month six watersheds were above the 60^th percentile. Temperatures for the 24-month period warmed above the 86^th percentile everywhere but the northwest, where they dropped slightly to the 78^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	5.71	CD1	74.34
Upper Colorado	70.27	CD2	81.42
Little Colorado	67.57	CD3	85.84
Verde	56.76	CD4	92.04
Bill Williams	45.95	CD5	84.96
Agua Fria	48.65	CD6	91.15
Lower Gila	70.27	CD7	92.04
Salt	70.27
Lower Colorado	56.76
Upper Gila	45.95
Santa Cruz	37.84
San Pedro	32.43
Willcox Playa	33.33
San Simon	51.35
White Water Draw	38.89

MAY 2008 – APRIL 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	5.88	CD1	77.68
Upper Colorado	44.44	CD2	86.61
Little Colorado	47.22	CD3	91.07
Verde	27.78	CD4	90.18
Bill Williams	11.11	CD5	92.86
Agua Fria	22.22	CD6	93.75
Lower Gila	52.78	CD7	97.32
Salt	47.22
Lower Colorado	38.89
Upper Gila	47.22
Santa Cruz	36.11
San Pedro	44.44
Willcox Playa	58.33
San Simon	38.89
White Water Draw	55.56

MAY 2007 – APRIL 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, especially in the eastern half of the state. All watersheds remain below the 35^th percentile, and nine watersheds are below the 15^th percentile. For temperature, the southeast climate divisions are above the 95^th percentile and even the coolest climate division, in the northwest, is above the 75^th percentile.

The 48-month period had very dry conditions in the southeast, near average conditions in central Arizona, and slightly wetter than average conditions in the northern and western watersheds. The Santa Cruz and San Pedro watersheds are at the 9^th and 12^th percentiles, respectively, while the upper and lower Colorado watersheds are at the 68^th and 76^th percentiles, respectively. Again, all climate divisions are above the 75^th percentile for temperature. The past four years have been much warmer than the average of the past 112 years.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	12.12	CD1	75.68
Upper Colorado	31.43	CD2	89.19
Little Colorado	14.29	CD3	90.99
Verde	11.43	CD4	94.59
Bill Williams	2.86	CD5	87.39
Agua Fria	5.71	CD6	97.30
Lower Gila	28.57	CD7	100.00
Salt	14.29
Lower Colorado	28.57
Upper Gila	11.43
Santa Cruz	8.57
San Pedro	20.00
Willcox Playa	31.43
San Simon	8.57
White Water Draw	34.29

MAY 2006 – APRIL 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	45.16	CD1	75.45
Upper Colorado	67.65	CD2	89.09
Little Colorado	35.29	CD3	88.18
Verde	55.88	CD4	94.55
Bill Williams	38.24	CD5	85.45
Agua Fria	35.29	CD6	93.64
Lower Gila	58.82	CD7	99.09
Salt	44.12
Lower Colorado	76.47
Upper Gila	32.35
Santa Cruz