State Precipitation & Temperature Update for Arizona

Conditions through October 2006

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 12/10/2006. Note the San Pedro and Santa Cruz watersheds have preliminary data only.

Precipitation Percentiles by Watershed (through October 2006)

Temperature Percentiles by Climate Division (through October 2006)

SHORT TERM CONDITIONS: 1-6 MONTHS

October brought above-average rainfall to northwest Arizona, while the eastern half of the state had average rainfall, and the southwest watersheds had below average rainfall. Temperatures were below average in the northwest, average in the northeast, southeast, and southwest, and slightly above average in the central climate division. For the 3-month period of August through October, precipitation was above average everywhere in the state except the Virgin, Bill Williams, Santa Cruz, and San Simon watersheds which had average rainfall. The temperatures ranged from below average in the northwest and southeast to above average in the northeast and southwest. The 6-month period, May through October, which includes the wet monsoon, is still well above average for the southeast watershed, and above average for the rest of the state, except Bill Williams at the 33^rd percentile. Temperatures were above the 75^th percentile everywhere in the state for the summer and above the 95^th percentile across the southern half of the state. The extreme temperatures generated an increased demand for the summer precipitation.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	77.78	CD1	54.46
Upper Colorado	91.67	CD2	34.82
Little Colorado	75.00	CD3	33.93
Verde	77.78	CD4	38.39
Bill Williams	77.78	CD5	56.25
Agua Fria	59.72	CD6	73.21
Lower Gila	38.89	CD7	49.11
Salt	72.22
Lower Colorado	77.78
Upper Gila	63.89
Santa Cruz	33.33
San Pedro	69.44
Willcox Playa	55.56
San Simon	16.67
White Water Draw	63.89

OCTOBER 2006: 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	52.94	CD1	68.30
Upper Colorado	75.00	CD2	16.07
Little Colorado	61.11	CD3	32.59
Verde	61.11	CD4	23.21
Bill Williams	41.67	CD5	73.21
Agua Fria	77.78	CD6	67.86
Lower Gila	66.67	CD7	25.00
Salt	75.00
Lower Colorado	69.44
Upper Gila	77.78
Santa Cruz	50.00
San Pedro	75.00
Willcox Playa	86.11
San Simon	50.00
White Water Draw	83.33

AUGUST 2006 - OCTOBER 2006 (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	45.59	CD1	83.04
Upper Colorado	63.89	CD2	83.48
Little Colorado	72.22	CD3	91.96
Verde	61.11	CD4	79.46
Bill Williams	33.33	CD5	97.32
Agua Fria	58.33	CD6	97.32
Lower Gila	61.11	CD7	98.21
Salt	69.44
Lower Colorado	69.44
Upper Gila	83.33
Santa Cruz	77.78
San Pedro	94.44
Willcox Playa	100.00
San Simon	61.11
White Water Draw	80.00

MAY 2005 – OCTOBER 2006 (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 is the most graphic indicator of the exceptionally dry winter of 2005, where most of the state had precipitation below the 25^th percentile, and many watersheds in the west central part of the state were below the 15^th percentile. The southeast fared only slightly better, with the San Pedro and Willcox as the only watersheds above the 50^th percentile, mostly as a result of a very wet monsoon. The corresponding temperatures for the 1-year period remain extremely high, above the 85^th percentile everywhere except the Colorado Plateau, which is above the 75^th percentile. The southeast and south central areas were above the 95^th percentile.

In contrast, the 2-year period shows the Colorado and Virgin River watersheds above the 75^th percentile, and most of the rest of the state near or slightly above average, except the Santa Cruz and San Simon watersheds, which are at the 21^st percentile. The 24-month temperatures were well above the 85th percentile everywhere except the Colorado Plateau, which dropped down to the 72^nd percentile. The southeast climate division remains at the 99^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	27.27	CD1	75.68
Upper Colorado	20.00	CD2	89.19
Little Colorado	20.00	CD3	89.19
Verde	14.29	CD4	92.79
Bill Williams	8.57	CD5	91.89
Agua Fria	14.29	CD6	95.50
Lower Gila	14.29	CD7	99.10
Salt	17.14
Lower Colorado	22.86
Upper Gila	34.29
Santa Cruz	17.14
San Pedro	62.86
Willcox Playa	58.82
San Simon	11.43
White Water Draw	48.57

OCTOBER 2005 – OCTOBER 2006 (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	90.32	CD1	72.73
Upper Colorado	79.41	CD2	90.91
Little Colorado	52.94	CD3	90.00
Verde	64.71	CD4	91.82
Bill Williams	58.82	CD5	88.18
Agua Fria	64.71	CD6	92.73
Lower Gila	67.65	CD7	99.09
Salt	55.88
Lower Colorado	82.35
Upper Gila	58.82
Santa Cruz	20.59
San Pedro	47.06
Willcox Playa	58.82
San Simon	20.59
White Water Draw	55.88

OCTOBER 2004 – OCTOBER 2006 (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 rankings have changed little since the October update, with the western half of the state remaining near or above-average, while the eastern half of the state is near or below-average, with the Santa Cruz and San Simon watersheds continuing to be the driest. There is no change in the 36-month temperatures, with the entire state still above the 75^th percentile. Climate divisions 4 and 7 in the southeast remain above the 95^th percentile for temperature.

The 48-month precipitation shows slight improvement, particularly in the southern half of the state. The western watersheds are near or above-normal while the eastern watersheds are near or below-normal. The driest are the Little Colorado, Santa Cruz, San Simon and Willcox Playa. Recent months of monsoon moisture have not changed the excessive heat pattern evident over the past 4 years. Temperatures continue to be above the 95^th percentile in the southeast and south central climate divisions, and above the 75^th percentile elsewhere in the state.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	93.55	CD1	76.15
Upper Colorado	69.70	CD2	89.91
Little Colorado	36.36	CD3	88.99
Verde	54.55	CD4	95.41
Bill Williams	57.58	CD5	88.07
Agua Fria	45.45	CD6	93.58
Lower Gila	60.61	CD7	99.08
Salt	48.48
Lower Colorado	84.85
Upper Gila	54.55
Santa Cruz	12.12
San Pedro	36.36
Willcox Playa	51.52
San Simon	18.18
White Water Draw	51.52

OCTOBER 2003 – OCTOBER 2006 (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	78.70
Upper Colorado	68.75	CD2	90.74
Little Colorado	21.88	CD3	94.44
Verde	56.25	CD4	97.22
Bill Williams	56.25	CD5	92.59
Agua Fria	40.62	CD6	97.22
Lower Gila	62.50	CD7	100.00
Salt	37.50
Lower Colorado	81.25
Upper Gila	28.12
Santa Cruz	15.62
San Pedro	28.12
Willcox Playa	18.75
San Simon	25.00
White Water Draw	28.12

OCTOBER 2002 – OCTOBER 2006 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

October 2006 Arizona Drought Update based on Precipitation (data through October 2006)

The following summary describes the heat and dryness across the state for the 1-, 3-, 6-, 12-, 24-, 36-, and 48-month periods. The Virgin River watershed has not yet reported precipitation data, and the Santa Cruz watershed has only a few stations reporting so far, so the results are preliminary.

SUMMARY

October brought above-average rainfall to northwest Arizona, while the eastern half of the state had average rainfall, and the southwest watersheds had below average rainfall. Temperatures were below average in the northwest, average in the northeast, southeast, and southwest, and slightly above average in the central climate division.

Three-month period – Precipitation was above average everywhere in the state except the Virgin, Bill Williams, Santa Cruz, and San Simon watersheds which had average rainfall. The temperatures ranged from below average in the northwest and southeast to above average in the northeast and southwest.

Six-month period – is still well above average for the southeast watershed, and above average for the rest of the state, except Bill Williams at the 33^rd percentile. Temperatures were above the 75^th percentile everywhere in the state for the summer and above the 95^th percentile across the southern half of the state. The extreme temperatures generated an increased demand for the summer precipitation.

Twelve-month period - is the most graphic indicator of the exceptionally dry winter of 2005, where most of the state had precipitation below the 25^th percentile, and many watersheds in the west central part of the state were below the 15^th percentile. The southeast fared only slightly better, with the San Pedro and Willcox as the only watersheds above the 50^th percentile, mostly as a result of a very wet monsoon. The corresponding temperatures for the 1-year period remain extremely high, above the 85^th percentile everywhere except the Colorado Plateau, which is above the 75^th percentile. The southeast and south central areas were above the 95^th percentile.

Two-year period - shows the Colorado and Virgin River watersheds above the 75^th percentile, and most of the rest of the state near or slightly above average, except the Santa Cruz and San Simon watersheds, which are at the 21^st percentile. The 24-month temperatures were well above the 85th percentile everywhere except the Colorado Plateau, which dropped down to the 72^nd percentile. The southeast climate division remains at the 99^th percentile.

Three-year period - has changed little since the October update, with the western half of the state remaining near or above-average, while the eastern half of the state is near or below-average, with the Santa Cruz and San Simon watersheds continuing to be the driest. There is no change in the 36-month temperatures, with the entire state still above the 75^th percentile. Climate divisions 4 and 7 in the southeast remain above the 95^th percentile for temperature.

Four-year period - shows slight improvement, particularly in the southern half of the state. The western watersheds are near or above-normal while the eastern watersheds are near or below-normal. The driest are the Little Colorado, Santa Cruz, San Simon and Willcox Playa. Recent months of monsoon moisture have not changed the excessive heat pattern evident over the past 4 years. Temperatures continue to be above the 95^th percentile in the southeast and south central climate divisions, and above the 75^th percentile elsewhere in the state.