State Precipitation & Temperature Update for Arizona

Conditions through March 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 04/24/2008. The data are preliminary.

Precipitation Percentiles by Watershed (through March 2008)

Temperature Percentiles by Climate Division (through March 2008)

SHORT TERM CONDITIONS: 1-6 MONTHS

March was extremely dry across the entire state. Precipitation was below the 15^th percentile for all watersheds except the upper Colorado, Virgin and lower Gila. Only one significant winter storm moved through the state during March. Temperatures were only slightly above average for the month across most of the state, except in the southwest corner which had temperatures above the 85^th percentile. The three-month winter period of January through March was wetter than average across the northwest 2/3 of the state, and drier than average in the southeastern third of the state. Virtually all of that precipitation fell in January and February. The three month period was near average in central and northwestern Arizona, warmer than average in southern Arizona, and colder than average in northeast Arizona. The cooler temperatures in the higher elevations helped to maintain the snowpack this year. The 6-month period precipitation, from October through March, was near- to slightly above-average in most watersheds. The northwest and southeast corners of the state saw few winter storms and received below average precipitation this winter. The northern half of the state had winter temperatures between the 61^st and 71^st percentile, while the southern half of the state had temperatures between the 78^th and 90^th percentiles. Overall, the temperature conditions matched the Climate Prediction Center’s forecast of a warmer than average winter.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	18.42	CD1	72.37
Upper Colorado	26.32	CD2	65.79
Little Colorado	10.53	CD3	74.56
Verde	10.53	CD4	82.89
Bill Williams	13.16	CD5	85.09
Agua Fria	13.16	CD6	82.89
Lower Gila	15.79	CD7	64.91
Salt	5.26
Lower Colorado	7.89
Upper Gila	7.89
Santa Cruz	13.16
San Pedro	10.53
Willcox Playa	10.53
San Simon	13.16
White Water Draw	5.26

MARCH 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	35.14	CD1	55.26
Upper Colorado	76.32	CD2	34.65
Little Colorado	62.16	CD3	44.30
Verde	60.53	CD4	64.04
Bill Williams	60.53	CD5	61.84
Agua Fria	57.89	CD6	57.89
Lower Gila	60.53	CD7	61.40
Salt	65.79
Lower Colorado	50.00
Upper Gila	39.47
Santa Cruz	34.21
San Pedro	23.68
Willcox Playa	18.92
San Simon	47.37
White Water Draw	18.92

JANUARY 2008 - MARCH 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	34.29	CD1	62.28
Upper Colorado	70.27	CD2	61.40
Little Colorado	55.56	CD3	67.54
Verde	58.33	CD4	89.47
Bill Williams	48.65	CD5	70.18
Agua Fria	56.76	CD6	78.95
Lower Gila	67.57	CD7	82.46
Salt	64.86
Lower Colorado	51.35
Upper Gila	45.95
Santa Cruz	51.35
San Pedro	40.00
Willcox Playa	30.56
San Simon	62.16
White Water Draw	33.33

OCTOBER 2008 – MARCH 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	8.57	CD1	76.99
Upper Colorado	72.97	CD2	82.74
Little Colorado	64.86	CD3	90.27
Verde	54.05	CD4	93.81
Bill Williams	45.95	CD5	88.50
Agua Fria	45.95	CD6	95.58
Lower Gila	75.68	CD7	96.46
Salt	70.27
Lower Colorado	59.46
Upper Gila	51.35
Santa Cruz	35.14
San Pedro	35.14
Willcox Playa	36.11
San Simon	56.76
White Water Draw	41.67

APRIL 2008 – MARCH 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	8.82	CD1	77.68
Upper Colorado	44.44	CD2	90.18
Little Colorado	55.56	CD3	92.86
Verde	30.56	CD4	91.96
Bill Williams	13.89	CD5	92.86
Agua Fria	25.00	CD6	93.75
Lower Gila	52.78	CD7	97.32
Salt	47.22
Lower Colorado	41.67
Upper Gila	47.22
Santa Cruz	33.33
San Pedro	44.44
Willcox Playa	58.33
San Simon	38.89
White Water Draw	58.33

APRIL 2007 – MARCH 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 period with all watersheds below the 35^th percentile. Nine watersheds are below the 22^nd percentile with seven below the 15^th percentile. The Northwest climate division is above the 75^th percentile and the other six climate divisions are above the 88^th percentile. Division 7 had its warmest 4-year period since 1895.

The 48-month period continues to have above-average precipitation in the western watersheds, below-average precipitation in the southeastern watersheds, and near- average precipitation in the central watersheds. Santa Cruz and San Pedro continue to be the driest long-term watersheds, and this month the lower Gila dropped below the 40^th percentile. The upper and lower Colorado are the wettest watersheds, at the 76^th percentile. Only the northwest climate division of Mohave County remains below the 86^th percentile for temperature, though 48-month temperatures have dropped slightly since last month.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	21.21	CD1	75.23
Upper Colorado	31.43	CD2	88.29
Little Colorado	25.71	CD3	90.99
Verde	14.29	CD4	94.59
Bill Williams	5.71	CD5	88.29
Agua Fria	5.71	CD6	97.30
Lower Gila	28.57	CD7	100.00
Salt	14.29
Lower Colorado	25.71
Upper Gila	14.29
Santa Cruz	8.57
San Pedro	20.00
Willcox Playa	31.43
San Simon	8.57
White Water Draw	34.29

APRIL 2006 – MARCH 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	61.29	CD1	75.45
Upper Colorado	76.47	CD2	88.18
Little Colorado	44.12	CD3	87.73
Verde	58.82	CD4	95.45
Bill Williams	50.00	CD5	86.36
Agua Fria	47.06	CD6	91.82
Lower Gila	61.76	CD7	99.09
Salt	47.06
Lower Colorado	76.47
Upper Gila	35.29
Santa Cruz	8.82
San Pedro	14.71
Willcox Playa	41.18
San Simon	29.41
White Water Draw	47.06

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

April 2008 Arizona Drought Update based on precipitation data through March 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 winter period of January through March was wetter than average across the northwest 2/3 of the state, and drier than average in the southeastern third of the state. Virtually all of that precipitation fell in January and February. The three month period was near average in central and northwestern Arizona, warmer than average in southern Arizona, and colder than average in northeast Arizona. The cooler temperatures in the higher elevations helped to maintain the snowpack this year.

The 6-month period precipitation, from October through March, was near- to slightly above-average in most watersheds. The northwest and southeast corners of the state saw few winter storms and received below average precipitation this winter. The northern half of the state had winter temperatures between the 61^st and 71^st percentile, while the southern half of the state had temperatures between the 78^th and 90^th percentiles. Overall, the temperature conditions matched the Climate Prediction Center’s forecast of a warmer than average winter.