State Precipitation & Temperature Update for Arizona

Conditions through September 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 10/20/2008. The data are preliminary.

Precipitation Percentiles by Watershed (through September 2008)

Temperature Percentiles by Climate Division (through September 2008)

SHORT TERM CONDITIONS: 1-6 MONTHS

September was much drier than average across northern and southeastern Arizona, and near average on the Gila, Santa Cruz and Lower Colorado watersheds. It was a very dry end to a wet monsoon. Temperatures were near average in the southeast, and above average elsewhere in the state. The three month period shows how wet the monsoon season was, with the southern half of the state above the 75^th percentile. The Little Colorado watershed was drier than average for the monsoon season, and the lower Colorado was near average. The wet conditions kept temperatures below average in southeastern Arizona, but the western half of the state was much warmer than average during the monsoon. The six-month period precipitation, from April through September, was also well above average in the southern half of the state and near or below average in the northern half of the state. Six month temperatures were only slightly above average across most of the state, but above the 88^th percentile in Maricopa, Pinal, La Paz and Yuma counties.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	8.33	CD1	82.89
Upper Colorado	28.95	CD2	68.42
Little Colorado	18.42	CD3	70.18
Verde	26.32	CD4	64.04
Bill Williams	21.05	CD5	87.72
Agua Fria	31.58	CD6	92.98
Lower Gila	52.63	CD7	59.65
Salt	28.95
Lower Colorado	42.11
Upper Gila	52.63
Santa Cruz	42.11
San Pedro	31.58
Willcox Playa	28.95
San Simon	39.47
White Water Draw	36.84

SEPTEMBER 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	13.89	CD1	90.27
Upper Colorado	68.42	CD2	81.58
Little Colorado	39.47	CD3	85.96
Verde	60.53	CD4	69.30
Bill Williams	57.89	CD5	92.98
Agua Fria	50.00	CD6	90.35
Lower Gila	94.74	CD7	38.60
Salt	89.47
Lower Colorado	57.89
Upper Gila	97.37
Santa Cruz	84.21
San Pedro	92.11
Willcox Playa	86.84
San Simon	89.47
White Water Draw	75.68

JULY 2008 - SEPTEMBER 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	2.78	CD1	73.45
Upper Colorado	55.26	CD2	68.42
Little Colorado	36.84	CD3	78.95
Verde	42.11	CD4	48.25
Bill Williams	52.63	CD5	88.60
Agua Fria	47.37	CD6	90.35
Lower Gila	94.74	CD7	65.79
Salt	81.58
Lower Colorado	56.58
Upper Gila	92.11
Santa Cruz	78.95
San Pedro	94.74
Willcox Playa	73.68
San Simon	89.47
White Water Draw	62.16

APRIL 2008 – SEPTEMBER 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 precipitation was near or above average everywhere except the Virgin River watershed. Seven watersheds were near average, and seven were above the 62^nd percentile. The 12 month period is the wettest period of the previous four years, due to the combination of a wet winter and a wet monsoon season. Temperatures remained warmer than average across the state, with the warmest conditions in the south.

The 24-month period had one watershed (lower Gila) with above average precipitation, seven watersheds near average, and seven watersheds below average. Temperatures for the 24-month period continue to be above the 75^th percentile across the state, and above the 85^th percentile in the southern half of Arizona.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	11.43	CD1	72.57
Upper Colorado	62.16	CD2	63.72
Little Colorado	43.24	CD3	78.76
Verde	51.35	CD4	73.01
Bill Williams	40.54	CD5	79.65
Agua Fria	48.65	CD6	86.28
Lower Gila	86.49	CD7	85.84
Salt	75.68
Lower Colorado	45.95
Upper Gila	72.97
Santa Cruz	62.16
San Pedro	64.86
Willcox Playa	50.00
San Simon	83.78
White Water Draw	48.65

OCTOBER 2008 – SEPTEMBER 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	3.03	CD1	75.00
Upper Colorado	55.56	CD2	83.93
Little Colorado	33.33	CD3	86.61
Verde	27.78	CD4	83.04
Bill Williams	19.44	CD5	89.29
Agua Fria	19.44	CD6	94.64
Lower Gila	77.78	CD7	94.64
Salt	52.78
Lower Colorado	36.11
Upper Gila	58.33
Santa Cruz	27.78
San Pedro	41.67
Willcox Playa	44.44
San Simon	52.78
White Water Draw	47.22

OCTOBER 2007 – SEPTEMBER 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 is still the driest period statewide, with the southeast watersheds near average, and the northern half of the state well below average for precipitation. Ten watersheds are below the 40^th percentile, and six are below the 25^th percentile. Temperatures for the three year period were very warm, with six of the seven climate divisions above the 87^th percentile. The southeast climate division continues to be the warmest in 112 years.

The 48-month period has nine watersheds with near average, three watersheds (San Simon, Santa Cruz, and San Pedro) with below average precipitation, and three watersheds (upper and lower Colorado and lower Gila) with above average precipitation. The driest areas are in southern Arizona, with the Santa Cruz the driest, below the 24^th percentile. The 48-month temperatures continue to be well above average, with all climate divisions above the 75^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	6.06	CD1	78.38
Upper Colorado	28.57	CD2	87.84
Little Colorado	20.00	CD3	89.19
Verde	11.43	CD4	92.79
Bill Williams	8.57	CD5	90.99
Agua Fria	8.57	CD6	98.20
Lower Gila	57.14	CD7	100.00
Salt	28.57
Lower Colorado	25.71
Upper Gila	45.71
Santa Cruz	20.00
San Pedro	42.86
Willcox Playa	51.43
San Simon	28.57
White Water Draw	45.71

OCTOBER 2006 – SEPTEMBER 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	58.06	CD1	75.45
Upper Colorado	73.53	CD2	89.09
Little Colorado	44.12	CD3	88.18
Verde	55.88	CD4	93.64
Bill Williams	47.06	CD5	85.45
Agua Fria	44.12	CD6	97.27
Lower Gila	79.41	CD7	100.00
Salt	50.00
Lower Colorado	82.35
Upper Gila	47.06
Santa Cruz	23.53
San Pedro	38.24
Willcox Playa	44.12
San Simon	32.35
White Water Draw	50.00

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

October 2008 Arizona Drought Update (based on precipitation data through September 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 period shows how wet the monsoon season was, with the southern half of the state above the 75^th percentile. The Little Colorado watershed was drier than average for the monsoon season, and the lower Colorado was near average. The wet conditions kept temperatures below average in southeastern Arizona, but the western half of the state was much warmer than average during the monsoon.

The 6-month period precipitation, from April through September, was also well above average in the southern half of the state and near or below average in the northern half of the state. Six month temperatures were only slightly above average across most of the state, but above the 88^th percentile in Maricopa, Pinal, La Paz and Yuma counties.