State Precipitation & Temperature Update for Arizona

Conditions through January 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 03/16/2009. The data are preliminary.

Precipitation Percentiles by Watershed (through January 2009)

Temperature Percentiles by Climate Division (through January 2009)

SHORT TERM CONDITIONS: 1-6 MONTHS

January was unusually dry across the entire state, with the driest conditions in the Bill Williams and lower Colorado watersheds. Three moderate winter storms moved through the state between the 7^th and the 17^th of the month, but precipitation totals in northern and southern Arizona were generally less than an inch, except at the higher elevations. Central Arizona had snow and rain amounts between 1 and 3 inches. Temperatures were above the 95^th percentile in Maricopa, Pinal, Yuma and La Paz counties. The three-month period of December through January was much wetter than average for all but the southeastern third of the state. The two driest watersheds, Santa Cruz and Willcox Playa were below the 36^th percentile. Temperatures for the three month period were well above average everywhere, with all counties, except Gila, above the 81^st percentile. The six-month period precipitation is much less homogeneously distributed. The northern watersheds, had near average precipitation, although the Virgin River watershed was very dry at the 14^th percentile, and the Little Colorado River watershed was just below the 30^th percentile. The southeastern watersheds were drier than average, while the Salt, lower Gila and San Simon watersheds in central and southwestern Arizona were slightly wetter than average during the last six months. Again, only Gila County had near average temperatures for the past six months. Maricopa, Pinal, La Paz and Yuma County had very warm temperatures, above the 97^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	39.47	CD1	92.17
Upper Colorado	33.33	CD2	84.35
Little Colorado	39.47	CD3	92.17
Verde	28.21	CD4	92.17
Bill Williams	23.08	CD5	95.65
Agua Fria	28.21	CD6	95.65
Lower Gila	33.33	CD7	93.91
Salt	43.59
Lower Colorado	12.82
Upper Gila	38.46
Santa Cruz	38.46
San Pedro	35.90
Willcox Playa	38.46
San Simon	38.46
White Water Draw	36.84

JANUARY 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	55.56	CD1	81.74
Upper Colorado	76.32	CD2	85.22
Little Colorado	70.27	CD3	83.48
Verde	70.27	CD4	69.13
Bill Williams	65.79	CD5	93.04
Agua Fria	71.05	CD6	91.30
Lower Gila	71.05	CD7	84.35
Salt	78.95
Lower Colorado	78.95
Upper Gila	50.00
Santa Cruz	36.84
San Pedro	47.22
Willcox Playa	40.54
San Simon	52.63
White Water Draw	35.14

NOVEMBER 2008 - JANUARY 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	14.29	CD1	81.74
Upper Colorado	57.89	CD2	81.74
Little Colorado	29.73	CD3	85.22
Verde	48.65	CD4	51.30
Bill Williams	52.63	CD5	97.39
Agua Fria	42.11	CD6	98.26
Lower Gila	60.53	CD7	72.17
Salt	71.05
Lower Colorado	55.26
Upper Gila	42.11
Santa Cruz	34.21
San Pedro	36.11
Willcox Playa	18.92
San Simon	60.53
White Water Draw	29.73

AUGUST 2008 – JANUARY 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 very mixed across the state, just like the six month period. Northern Arizona was generally drier than average, while southern Arizona was wetter in the west and drier than average in the east. This reflects the dry fall and winter in southern Arizona, as the summer was very wet in the southeastern watersheds. Gila County continues to be the only area with near average temperatures for the previous year. The northern half of the state was slightly warmer than average, while the southern half of the state was much warmer than average.

The 24 month period is the wettest long-term period, but is inconsistent from watershed to watershed. Seven watersheds in central and southern Arizona had slightly below average precipitation over the last two years, while five watersheds in north, east central and southwest Arizona were wetter than average. Three watersheds had near average precipitation. Temperatures in the past two years have been well above average in all areas of the state, with the warmest temperatures in Maricopa and Pinal counties.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	5.56	CD1	73.68
Upper Colorado	57.89	CD2	71.93
Little Colorado	23.68	CD3	82.46
Verde	26.32	CD4	43.86
Bill Williams	31.58	CD5	94.74
Agua Fria	23.68	CD6	98.25
Lower Gila	76.32	CD7	83.77
Salt	71.05
Lower Colorado	52.63
Upper Gila	55.26
Santa Cruz	36.84
San Pedro	55.26
Willcox Playa	34.21
San Simon	60.53
White Water Draw	40.54

FEBRUARY 2008 – JANUARY 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	76.99
Upper Colorado	72.97	CD2	90.27
Little Colorado	48.65	CD3	88.50
Verde	37.84	CD4	82.30
Bill Williams	29.73	CD5	92.92
Agua Fria	32.43	CD6	98.23
Lower Gila	81.08	CD7	94.69
Salt	81.08
Lower Colorado	51.35
Upper Gila	62.16
Santa Cruz	32.43
San Pedro	43.24
Willcox Playa	37.84
San Simon	62.16
White Water Draw	35.14

FEBRUARY 2007 – JANUARY 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 shows the upper and Little Colorado River watersheds had near average precipitation, while the Bill Williams, Verde and Agua Fria watersheds, also in northern Arizona had much lower than average precipitation. In southern Arizona, the upper and lower Gila, Salt and Willcox watersheds were wetter than average, but the Santa Cruz and lower Colorado were slightly drier than average. Five watersheds across the state were near average for precipitation. Temperatures over the three-year period remain extremely high with only the northwest climate division below the 84^th percentile, and the southern climate divisions above the 97^th percentile.

The 48-month period became the driest period last month, and it continues to be the driest period as the winter of 2008-2009 replaces the winter of 2004-2005. Six watersheds are below the 25^th percentile, five watersheds are between the 25^th and 40^th percentile, and four watersheds are above the 40^th percentile. The four-year temperatures continue to be extremely high, with the southern third of the state above the 99^th percentile, and the coolest climate division, Mohave County in the northwest, still above the 75^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	5.88	CD1	76.79
Upper Colorado	44.44	CD2	88.39
Little Colorado	52.78	CD3	88.39
Verde	25.00	CD4	84.82
Bill Williams	11.11	CD5	91.96
Agua Fria	16.67	CD6	97.32
Lower Gila	69.44	CD7	98.21
Salt	63.89
Lower Colorado	33.33
Upper Gila	63.89
Santa Cruz	27.78
San Pedro	58.33
Willcox Playa	61.11
San Simon	44.44
White Water Draw	50.00

FEBRUARY 2006 – JANUARY 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	25.00	CD1	75.68
Upper Colorado	48.57	CD2	90.09
Little Colorado	31.43	CD3	87.39
Verde	20.00	CD4	90.99
Bill Williams	8.57	CD5	90.09
Agua Fria	8.57	CD6	99.10
Lower Gila	60.00	CD7	100.00
Salt	54.29
Lower Colorado	40.00
Upper Gila	42.86
Santa Cruz	11.43
San Pedro	31.43
Willcox Playa	31.43
San Simon	14.29
White Water Draw	37.14

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

February 2008 Arizona Drought Update based on precipitation data through January 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

January was unusually dry across the entire state, with the driest conditions in the Bill Williams and lower Colorado watersheds. Three moderate winter storms moved through the state between the 7^th and the 17^th of the month, but precipitation totals in northern and southern Arizona were generally less than an inch, except at the higher elevations. Central Arizona had snow and rain amounts between 1 and 3 inches. Temperatures were above the 95^th percentile in Maricopa, Pinal, Yuma and La Paz counties.

The 3-month period of December through January was much wetter than average for all but the southeastern third of the state. The two driest watersheds, Santa Cruz and Willcox Playa were below the 36^th percentile. Temperatures for the three month period were well above average everywhere, with all counties, except Gila, above the 81^st percentile.

The 6-month period precipitation is much less homogeneously distributed. The northern watersheds, had near average precipitation, although the Virgin River watershed was very dry at the 14^th percentile, and the Little Colorado River watershed was just below the 30^th percentile. The southeastern watersheds were drier than average, while the Salt, lower Gila and San Simon watersheds in central and southwestern Arizona were slightly wetter than average during the last six months. Again, only Gila County had near average temperatures for the past six months. Maricopa, Pinal, La Paz and Yuma County had very warm temperatures, above the 97^th percentile.

The 12-month period precipitation was very mixed across the state, just like the six month period. Northern Arizona was generally drier than average, while southern Arizona was wetter in the west and drier than average in the east. This reflects the dry fall and winter in southern Arizona, as the summer was very wet in the southeastern watersheds. Gila County continues to be the only area with near average temperatures for the previous year. The northern half of the state was slightly warmer than average, while the southern half of the state was much warmer than average.

The 24 month period is the wettest long-term period, but is inconsistent from watershed to watershed. Seven watersheds in central and southern Arizona had slightly below average precipitation over the last two years, while five watersheds in north, east central and southwest Arizona were wetter than average. Three watersheds had near average precipitation. Temperatures in the past two years have been well above average in all areas of the state, with the warmest temperatures in Maricopa and Pinal counties.

The 36-month period shows the upper and Little Colorado River watersheds had near average precipitation, while the Bill Williams, Verde and Agua Fria watersheds, also in northern Arizona had much lower than average precipitation. In southern Arizona, the upper and lower Gila, Salt and Willcox watersheds were wetter than average, but the Santa Cruz and lower Colorado were slightly drier than average. Five watersheds across the state were near average for precipitation. Temperatures over the three-year period remain extremely high with only the northwest climate division below the 84^th percentile, and the southern climate divisions above the 97^th percentile.

The 48-month period became the driest period last month, and it continues to be the driest period as the winter of 2008-2009 replaces the winter of 2004-2005. Six watersheds are below the 25^th percentile, five watersheds are between the 25^th and 40^th percentile, and four watersheds are above the 40^th percentile. The four-year temperatures continue to be extremely high, with the southern third of the state above the 99^th percentile, and the coolest climate division, Mohave County in the northwest, still above the 75^th percentile.