State Precipitation & Temperature Update for Arizona

Conditions through February 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 3/30/2007. The data are preliminary.

Precipitation Percentiles by Watershed (through February 2007)

Temperature Percentiles by Climate Division (through February 2007)

SHORT TERM CONDITIONS: 1-6 MONTHS

February precipitation was below average everywhere in the state, and below the 25^th percentile in the northern and western watersheds. In contrast to January, the storm tracks across the southern part of the state dropped little precipitation in Arizona. Temperatures were only slightly above average across most of the state, with the warmest temperatures in the northwest. The 3-month period of December through February was below the 25^th percentile for the southwest deserts and the upper Colorado River basin, and below the 52^nd percentile across the rest of the state. This was very unexpected for a moderate El Niño year, when the December-February precipitation is generally above normal. Due to the exceptionally cold December and colder than normal January, temperatures over the 3-month period were slightly below average for most of the state. Unfortunately, the cold temperatures were not accompanied by precipitation, so the snowpack was well below average. Precipitation for the fall and winter, represented by the 6-month period of September through February, was very dry, below the 40^th percentile, throughout the state. Particularly hard hit were the Verde, Bill Williams, Agua Fria, Santa Cruz and San Simon watersheds, with precipitation below the 23rd percentile. Temperatures across the state were near to slightly above average everywhere except the Colorado Plateau in the northeast, where cooler temperatures prevailed for the 6-month period.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	21.62	CD1	84.51
Upper Colorado	24.32	CD2	69.47
Little Colorado	35.14	CD3	61.06
Verde	24.32	CD4	71.24
Bill Williams	22.97	CD5	62.83
Agua Fria	32.43	CD6	74.34
Lower Gila	29.73	CD7	55.31
Salt	37.84
Lower Colorado	24.32
Upper Gila	35.14
Santa Cruz	29.73
San Pedro	27.03
Willcox Playa	27.78
San Simon	29.73
White Water Draw	24.32

FEBRUARY 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	40.00	CD1	61.06
Upper Colorado	19.44	CD2	49.56
Little Colorado	31.43	CD3	46.02
Verde	25.71	CD4	51.33
Bill Williams	8.33	CD5	40.27
Agua Fria	30.56	CD6	46.02
Lower Gila	22.22	CD7	21.24
Salt	36.11
Lower Colorado	13.89
Upper Gila	44.44
Santa Cruz	19.44
San Pedro	38.24
Willcox Playa	42.86
San Simon	16.67
White Water Draw	51.43

DECEMBER 2006 - FEBRUARY 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	33.33	CD1	69.03
Upper Colorado	36.11	CD2	39.38
Little Colorado	28.57	CD3	52.21
Verde	22.86	CD4	45.58
Bill Williams	19.44	CD5	60.62
Agua Fria	19.44	CD6	62.83
Lower Gila	27.78	CD7	66.37
Salt	27.78
Lower Colorado	41.67
Upper Gila	27.78
Santa Cruz	16.67
San Pedro	44.12
Willcox Playa	40.00
San Simon	16.67
White Water Draw	48.57

SEPTEMBER 2006 – FEBRUARY 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

The western half of the state experienced very dry conditions for the previous 12-month period, while the eastern half of the state had near to slightly above average precipitation. Due to a combination of an extremely wet monsoon and some southerly winter storm tracks, precipitation in the San Pedro watershed was almost at the 70^th percentile. Temperatures for the previous 12 months remain well above average, with the southeast climate division above the 96^th percentile.

The two-year period paints the bleakest picture of the drought status. With the exception of the Virgin River watershed, all areas of the state are below the 31^st percentile, and 10 watersheds are below the 12^th percentile. Hardest hit are the Bill Williams, Agua Fria and San Simon watersheds, which are all below the 3^rd percentile. This demonstrates how variable our precipitation can be, as this year had brought hopes of a wet winter due to El Niño. Again, only the northwest climate division is below the 75^th percentile for temperature, while the rest of the state was above the 84^th percentile. The southeast climate division remains the hot spot at the 99^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	38.24	CD1	74.11
Upper Colorado	33.33	CD2	71.43
Little Colorado	52.78	CD3	80.80
Verde	36.11	CD4	71.88
Bill Williams	11.11	CD5	84.82
Agua Fria	22.22	CD6	83.48
Lower Gila	25.00	CD7	96.43
Salt	52.78
Lower Colorado	33.33
Upper Gila	55.56
Santa Cruz	47.22
San Pedro	69.44
Willcox Playa	60.00
San Simon	25.00
White Water Draw	54.29

MARCH 2006 – FEBRUARY 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	48.48	CD1	72.97
Upper Colorado	11.43	CD2	85.59
Little Colorado	11.43	CD3	84.68
Verde	5.71	CD4	87.39
Bill Williams	2.86	CD5	84.68
Agua Fria	2.86	CD6	92.79
Lower Gila	5.71	CD7	99.10
Salt	5.71
Lower Colorado	28.57
Upper Gila	8.57
Santa Cruz	5.71
San Pedro	25.71
Willcox Playa	31.43
San Simon	2.86
White Water Draw	25.71

MARCH 2005 – FEBRUARY 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, which includes the wet winter of 2004-2005, remains only slightly above average for most of the state. The Virgin, upper and lower Colorado, and lower Gila watersheds are all well above normal. The southern watersheds are below the 40^th percentile, with the San Simon and Santa Cruz being the driest. The 36-month^-temperature pattern remains the same as last month’s update, with Gila County and the southeast climate division above the 95^th percentile for temperature, and the rest of the state above the 77^th percentile.

The 48-month precipitation pattern is quite representative of the drought conditions across the state, with one watershed above average, three watersheds near average and 10 watersheds below the 40^th percentile for precipitation. The driest conditions are in the eastern and southern parts of the state. The long-term temperature pattern still has all areas above the 75^th percentile, with the hottest temperatures in Gila County and the southeast climate division, both above the 96^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	78.12	CD1	74.55
Upper Colorado	67.65	CD2	89.09
Little Colorado	44.12	CD3	86.82
Verde	55.88	CD4	95.45
Bill Williams	52.94	CD5	87.27
Agua Fria	44.12	CD6	90.00
Lower Gila	61.76	CD7	99.09
Salt	44.12
Lower Colorado	79.41
Upper Gila	44.12
Santa Cruz	5.88
San Pedro	26.47
Willcox Playa	38.24
San Simon	8.82
White Water Draw	50.00

MARCH 2004 – FEBRUARY 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	77.06
Upper Colorado	54.55	CD2	89.91
Little Colorado	15.15	CD3	92.66
Verde	48.48	CD4	96.33
Bill Williams	42.42	CD5	89.91
Agua Fria	24.24	CD6	89.91
Lower Gila	39.39	CD7	99.08
Salt	27.27
Lower Colorado	69.70
Upper Gila	18.18
Santa Cruz	6.06
San Pedro	15.15
Willcox Playa	18.18
San Simon	12.12
White Water Draw	30.30

MARCH 2003 – FEBRUARY 2007 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

March 2007 Arizona Drought Update based on Precipitation (data through February 2007)

The following summary describes the heat and dryness across the state for the 1-, 3-, 6-, 12-, 24-, 36-, and 48-month periods.

SUMMARY

February - Precipitation was below average everywhere in the state, and below the 25^th percentile in the northern and western watersheds. In contrast to January, the storm tracks across the southern part of the state dropped little precipitation in Arizona. Temperatures were only slightly above average across most of the state, with the warmest temperatures in the northwest.

Three-month period – The 3-month period of December through February was below the 25^th percentile for the southwest deserts and the upper Colorado River basin, and below the 52^nd percentile across the rest of the state. This was very unexpected for a moderate El Niño year, when the December-February precipitation is generally above normal. Due to the exceptionally cold December and colder than normal January, temperatures over the 3-month period were slightly below average for most of the state. Unfortunately, the cold temperatures were not accompanied by precipitation, so the snowpack was well below average.

Six-month period – Precipitation for the fall and winter, represented by the 6-month period of September through February, was very dry, below the 40^th percentile, throughout the state. Particularly hard hit were the Verde, Bill Williams, Agua Fria, Santa Cruz and San Simon watersheds, with precipitation below the 23rd percentile. Temperatures across the state were near to slightly above average everywhere except the Colorado Plateau in the northeast, where cooler temperatures prevailed for the 6-month period.

Twelve-month period – The western half of the state experienced very dry conditions for the previous 12-month period, while the eastern half of the state had near to slightly above average precipitation. Due to a combination of an extremely wet monsoon and some southerly winter storm tracks, precipitation in the San Pedro watershed was almost at the 70^th percentile. Temperatures for the previous 12 months remain well above average, with the southeast climate division above the 96^th percentile.

Two-year period - The two-year period paints the bleakest picture of the drought status. With the exception of the Virgin River watershed, all areas of the state are below the 31^st percentile, and 10 watersheds are below the 12^th percentile. Hardest hit are the Bill Williams, Agua Fria and San Simon watersheds, which are all below the 3^rd percentile. This demonstrates how variable our precipitation can be, as this year had brought hopes of a wet winter due to El Niño. Again, only the northwest climate division is below the 75^th percentile for temperature, while the rest of the state was above the 84^th percentile. The southeast climate division remains the hot spot at the 99^th percentile.

Three-year period - The 36-month precipitation, which includes the wet winter of 2004-2005, remains only slightly above average for most of the state. The Virgin, upper and lower Colorado, and lower Gila watersheds are all well above normal. The southern watersheds are below the 40^th percentile, with the San Simon and Santa Cruz being the driest. The 36-month^-temperature pattern remains the same as last month’s update, with Gila County and the southeast climate division above the 95^th percentile for temperature, and the rest of the state above the 77^th percentile.

Four-year period - The 48-month precipitation pattern is quite representative of the drought conditions across the state, with one watershed above average, three watersheds near average and 10 watersheds below the 40^th percentile for precipitation. The driest conditions are in the eastern and southern parts of the state. The long-term temperature pattern still has all areas above the 75^th percentile, with the hottest temperatures in Gila County and the southeast climate division, both above the 96^th percentile.