State Precipitation & Temperature Update for Arizona

Conditions through February 2010

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 3/22/2010. The data are preliminary.

Precipitation Percentiles by Watershed (through February 2010)

Temperature Percentiles by Climate Division (through February 2010)

SHORT TERM CONDITIONS: 1-6 MONTHS

February precipitation was well above average everywhere in Arizona except the Little Colorado and San Simon watersheds, which were near normal. Temperatures in February were colder than average in eastern Arizona, and near or slightly warmer than average in western Arizona. The three-month period, December through February, was much wetter than normal, above the 76^th percentile, in all watersheds. Three-month temperatures were also cooler than average in the eastern half of the state, and near or slightly warmer than average in the western climate divisions. The coolest temperatures were in the southeastern counties. The six-month period precipitation, from September through February, was also wetter than average in all watersheds except the Little Colorado, which was near average at the 44^th percentile. All other watersheds were above the 60^th percentile. Temperatures were cooler than average across the Colorado Plateau, near average in the Yavapai, Gila, and southeastern counties. Maricopa, Pinal, La Paz and Yuma counties were warmer than average between the 75^th and 95^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	92.50	CD1	57.76
Upper Colorado	75.00	CD2	37.50
Little Colorado	42.50	CD3	46.55
Verde	62.50	CD4	38.36
Bill Williams	70.00	CD5	64.22
Agua Fria	70.00	CD6	68.53
Lower Gila	75.00	CD7	31.47
Salt	65.00
Lower Colorado	75.00
Upper Gila	75.00
Santa Cruz	75.00
San Pedro	92.50
Willcox Playa	82.05
San Simon	58.75
White Water Draw	80.00

FEBRUARY 2010: 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	89.47	CD1	56.96
Upper Colorado	94.87	CD2	25.22
Little Colorado	81.58	CD3	43.48
Verde	92.11	CD4	35.65
Bill Williams	92.31	CD5	66.96
Agua Fria	92.31	CD6	63.48
Lower Gila	92.31	CD7	22.61
Salt	87.18
Lower Colorado	92.31
Upper Gila	87.18
Santa Cruz	82.05
San Pedro	94.59
Willcox Playa	78.95
San Simon	76.92
White Water Draw	78.95

DECEMBER 2009 - FEBRUARY 2010 (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	75.00	CD1	68.70
Upper Colorado	84.62	CD2	25.22
Little Colorado	44.74	CD3	54.78
Verde	63.16	CD4	52.17
Bill Williams	74.36	CD5	75.22
Agua Fria	69.23	CD6	86.96
Lower Gila	71.79	CD7	57.39
Salt	74.36
Lower Colorado	82.05
Upper Gila	64.10
Santa Cruz	74.36
San Pedro	72.97
Willcox Playa	63.16
San Simon	74.36
White Water Draw	60.53

SEPTEMBER 2009 – FEBRUARY 2010 (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

While the 12-month period remains the driest short term period, it now has eight watersheds near average, two wetter than average, and only five watersheds drier than average. Temperatures were warmer than average in all climate divisions, except the Colorado Plateau, with the warmest conditions in Maricopa and Pinal Counties.

The 24-month period is now the driest long-term period, with drier than average conditions in nine watersheds. The driest watersheds, Virgin, Little Colorado and Verde were below the 21^st percentile. Only the lower Gila and lower Colorado watersheds were above the 60^th percentile. Temperatures for the 24-month period are slightly warmer than average across northern Arizona, near average in Gila County and much warmer than average in all other counties, with Maricopa and Pinal counties above the 97^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	37.84	CD1	71.30
Upper Colorado	64.10	CD2	52.17
Little Colorado	23.08	CD3	79.13
Verde	38.46	CD4	68.70
Bill Williams	33.33	CD5	86.09
Agua Fria	51.28	CD6	97.39
Lower Gila	64.10	CD7	80.87
Salt	51.28
Lower Colorado	58.97
Upper Gila	48.72
Santa Cruz	41.03
San Pedro	56.41
Willcox Playa	44.74
San Simon	30.77
White Water Draw	42.11

MARCH 2009 – FEBRUARY 2010 (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	8.33	CD1	71.05
Upper Colorado	39.47	CD2	65.79
Little Colorado	15.79	CD3	81.58
Verde	21.05	CD4	57.89
Bill Williams	36.84	CD5	92.11
Agua Fria	36.84	CD6	100.00
Lower Gila	73.68	CD7	78.95
Salt	52.63
Lower Colorado	60.53
Upper Gila	50.00
Santa Cruz	31.58
San Pedro	50.00
Willcox Playa	44.74
San Simon	50.00
White Water Draw	34.21

MARCH 2008 – FEBRUARY 2010 (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 is still the “wettest” of the long term intervals, with five watersheds wetter than average. However, there are also six watersheds drier than average in west central and southeastern Arizona. The driest watershed, the Virgin River, is below the 3^rd percentile, while the wettest watershed, the lower Gila, is above the 81^st percentile, and 4 watersheds are between the 40^th and 60^th percentiles. Climate division temperatures over the three-year period continue to be above the 79^th percentile, except Mohave County, which was slightly cooler, at the 72^nd percentile. Pinal and Maricopa Counties had temperatures at the 100^th percentile, the warmest since 1895.

The 48-month period is no longer the driest long-term period, as only six watersheds are drier than average, three watersheds are wetter than average, and six watersheds are near average. This shift occurred as February 2005, a very dry month has been replaced with February 2010, an extremely wet month. The four-year period continues to be the warmest interval, with all climate divisions above the 76^th percentile, and the southern half of the state, plus Yavapai County, above the 87^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	2.86	CD1	72.57
Upper Colorado	62.16	CD2	84.07
Little Colorado	45.95	CD3	89.38
Verde	37.84	CD4	79.20
Bill Williams	37.84	CD5	92.04
Agua Fria	35.14	CD6	100.00
Lower Gila	81.08	CD7	92.04
Salt	72.97
Lower Colorado	54.05
Upper Gila	64.86
Santa Cruz	29.73
San Pedro	59.46
Willcox Playa	37.84
San Simon	64.86
White Water Draw	40.54

MARCH 2007 – FEBRUARY 2010 (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	76.11
Upper Colorado	50.00	CD2	83.04
Little Colorado	41.67	CD3	87.50
Verde	27.78	CD4	78.57
Bill Williams	16.67	CD5	91.07
Agua Fria	16.67	CD6	100.00
Lower Gila	77.78	CD7	91.07
Salt	61.11
Lower Colorado	36.11
Upper Gila	61.11
Santa Cruz	33.33
San Pedro	58.33
Willcox Playa	55.56
San Simon	47.22
White Water Draw	50.00

MARCH 2006 – FEBRUARY 2010 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

March 2010 Arizona Drought Update (based on precipitation data through February 2010)

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, December through February, was much wetter than normal, above the 76^th percentile, in all watersheds. Three-month temperatures were also cooler than average in the eastern half of the state, and near or slightly warmer than average in the western climate divisions. The coolest temperatures were in the southeastern counties.

The 6-month period precipitation, from September through February, was also wetter than average in all watersheds except the Little Colorado, which was near average at the 44^th percentile. All other watersheds were above the 60^th percentile. Temperatures were cooler than average across the Colorado Plateau, near average in the Yavapai, Gila, and southeastern counties. Maricopa, Pinal, La Paz and Yuma counties were warmer than average between the 75^th and 95^th percentile.

The 12-month period remains the driest short term period, but it now has eight watersheds near average, two wetter than average, and only five watersheds drier than average. Temperatures were warmer than average in all climate divisions, except the Colorado Plateau, with the warmest conditions in Maricopa and Pinal Counties.