State Precipitation & Temperature Update for Arizona

Conditions through June 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 7 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 7 periods for precipitation and temperature are shown below, with tables of the percentile values and descriptive text following the maps. Values of -99 and grey shading indicate missing data. When the data are available, this product will be updated. Current update is 08/01/2006.

Precipitation Percentiles by Watershed (through June 2006)

Temperature Percentiles by Climate Division (through June 2006)

SHORT TERM CONDITIONS: 1-6 MONTHS

The month of June was characterized by above average precipitation across the entire state, although this should not imply a “wet” month, as normal precipitation for June is low. All watersheds except the Salt and Upper Gila were well above normal precipitation for the month. The Salt and Upper Gila were nearly normal. The month of June, 2006 was above the 98^th percentile for divisions 4, 5, and 6 across central Arizona, indicating that this past June was among the hottest Junes in the past 112 years. The Virgin River in the Northwest, the Lower Gila in the Southwest an the White Water Draw in the Southeast had nearly normal precipitation for the 3month period from April through June, while the Lower Colorado to the west and the San Simon River in the southwest had above normal precipitation for the past 3 months. All the other watersheds had well below normal precipitation from April through June. Temperatures were above the 95^th percentile in the Northeast, southeast and south-central portions of the state during the previous 3 months, and the rest of the state also had unusually high temperatures. The extremely dry winter is seen clearly in the precipitation percentiles for the past 6-month period, with all below the 20^th percentile except the Virgin River in the Arizona Strip. Temperatures for the winter were well above normal everywhere, with the northeast climate division on the Colorado Plateau being the highest above normal.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	78.57	CD1	92.86%
Upper Colorado	75.00	CD2	96.43%
Little Colorado	69.44	CD3	95.54%
Verde	72.22	CD4	98.21%
Bill Williams	86.11	CD5	99.11%
Agua Fria	75.00	CD6	98.21%
Lower Gila	94.44	CD7	93.75%
Salt	47.22
Lower Colorado	94.44
Upper Gila	47.22
Santa Cruz	-99
San Pedro	89.89
Willcox Playa	-99
San Simon	94.44
White Water Draw	63.89

JUNE 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	45.71	CD1	87.50%
Upper Colorado	30.56	CD2	98.21%
Little Colorado	30.56	CD3	93.75%
Verde	27.78	CD4	93.75%
Bill Williams	38.89	CD5	93.75%
Agua Fria	19.44	CD6	97.32%
Lower Gila	44.44	CD7	95.54%
Salt	27.78
Lower Colorado	72.22
Upper Gila	16.67
Santa Cruz	-99
San Pedro	33.33
Willcox Playa	-99
San Simon	66.67
White Water Draw	44.44

APRIL 2006 - JUNE 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	55.88	CD1	78.57%
Upper Colorado	19.44	CD2	95.54%
Little Colorado	14.29	CD3	89.29%
Verde	16.67	CD4	93.75%
Bill Williams	11.11	CD5	84.82%
Agua Fria	13.89	CD6	94.64%
Lower Gila	16.67	CD7	94.64%
Salt	19.44
Lower Colorado	16.67
Upper Gila	13.89
Santa Cruz	-99
San Pedro	11.11
Willcox Playa	-99
San Simon	16.67
White Water Draw	11.43

JANUARY 2005 – JUNE 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 intermediate time periods of 1- and 2-years show the importance of the historical context of drought. The 1-year period precipitation has been below the 15^th percentile for all watersheds except the 3 along our western border. The corresponding temperatures for the 1-year period have been among the highest ever, particularly in the southeast and south central climate divisions.

In stark contrast, the 2-year period shows very little evidence of drought across the western and central portions of the state, with precipitation totals well above normal. The Little Colorado and the southeastern watersheds show precipitation totals below the 30% percentile, with the driest watershed being the San Pedro. This 2-year period includes the extremely wet winter of 2005. Except for climate division 1 in the northwest, temperatures for the 2-year period were all at or above the 80^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	48.48	CD1	78.38%
Upper Colorado	11.43	CD2	91.89%
Little Colorado	11.43	CD3	91.89%
Verde	11.43	CD4	94.59%
Bill Williams	14.29	CD5	86.49%
Agua Fria	8.57	CD6	95.50%
Lower Gila	20.00	CD7	98.20%
Salt	8.57
Lower Colorado	31.43
Upper Gila	8.57
Santa Cruz	-99
San Pedro	5.71
Willcox Playa	-99
San Simon	5.71
White Water Draw	14.71

JULY 2005 – JUNE 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	96.88	CD1	72.73%
Upper Colorado	82.35	CD2	89.09%
Little Colorado	23.53	CD3	88.18%
Verde	70.59	CD4	92.73%
Bill Williams	73.53	CD5	80.00%
Agua Fria	55.88	CD6	88.18%
Lower Gila	67.65	CD7	95.45%
Salt	44.12
Lower Colorado	91.18
Upper Gila	32.35
Santa Cruz	-99
San Pedro	11.76
Willcox Playa	-99
San Simon	20.59
White Water Draw	26.47

JULY 2004 – JUNE 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 pattern of precipitation rankings for the longer-term 3-year period across the state is similar to that of the 2-year period, but includes another very dry winter from 2003-2004. Again, the western and northern watershed precipitation totals were at or above average. Across the eastern and south central watersheds, precipitation fell far below average. The Salt, Verde and Little Colorado watersheds had abnormally dry conditions, while the southeast watersheds had precipitation below the 20^th percentile. Except for the climate divisions along the Colorado River to the west, the rest of the state was warmer than 80% of the years, during the 3-year period. This 3-year period was the warmest on record for the southeastern division.

The length of the current drought and warming is more evident when looking at the longer 4-year period. Only the Upper and Lower Colorado, Bill Williams, and Lower Gila watersheds have had precipitation near or above normal during this period. The driest watersheds are again in the southeast and south central region. Along with the dryness has been excessive heat. Climate divisions 4, 6, and 7 in the south and south central areas have been above the 98^th percentile in the 4-year period, with division 7 having the hottest 4-year period on record.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	-99	CD1	78.90%
Upper Colorado	63.64	CD2	94.50%
Little Colorado	27.27	CD3	92.66%
Verde	51.52	CD4	97.25%
Bill Williams	60.61	CD5	87.16%
Agua Fria	36.36	CD6	96.33%
Lower Gila	60.61	CD7	100.00%
Salt	33.33
Lower Colorado	75.76
Upper Gila	12.12
Santa Cruz	-99
San Pedro	9.09
Willcox Playa	-99
San Simon	30.30
White Water Draw	18.18

JULY 2003 – JUNE 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	CD1	80.56%
Upper Colorado	62.50	CD2	91.67%
Little Colorado	21.88	CD3	96.30%
Verde	37.50	CD4	98.15%
Bill Williams	43.75	CD5	90.74%
Agua Fria	37.50	CD6	98.15%
Lower Gila	50.00	CD7	100.00%
Salt	21.88
Lower Colorado	75.00
Upper Gila	12.50
Santa Cruz	-99
San Pedro	6.25
Willcox Playa	-99
San Simon	18.75
White Water Draw	6.25

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

July 2006 Arizona Drought Update based on Precipitation (data through June 2006)

The following summary describes the drought conditions based only on precipitation. This practice of categorizing the drought in terms of precipitation only will be discontinued as the long term impacts of drought in Arizona are also dependent on stream-flow, soil moisture and temperature, which are not considered here.

SUMMARY

● The recent dry conditions that have existed since March continue in June, although the meager precipitation is statistically above the normal June rainfall for most of the state. The 1-month precipitation picture gives a false impression that the drought has been alleviated.

● Precipitation totals for the past 3- and 6-month periods are very low, with much of the state characterized by amounts indicative of “moderate” to “severe” short-term drought.

● The past 12 months have been marked by dryness characteristic of “severe” drought across 10 of the 15 Arizona watersheds, and dryness or “moderate” drought in the southwest.

● There is very little evidence of drought across the west, north and central watersheds of the state when examining precipitation totals for the past 2 years. Drought is evident in the Little Colorado and across southeastern Arizona during this period.

● The 36-month precipitation totals are at or above average for the 5 western watersheds in Arizona. However, across the eastern half of Arizona, the 3-year precipitation total is suggestive of “abnormally dry” to “severe drought”, with the hardest hit areas in the southeast.

● The long-term problematic areas within the state are the east-central and southeastern regions, where 4-year precipitation totals are suggestive of “severe drought” conditions.

Numerical Category	Description	Precipitation Percentile
0	No drought	40.01 – 100
1	abnormally dry	25.01 – 40.00
2	moderate drought	15.01 – 25.00
3	severe drought	5.01 – 15.00
4	extreme drought	0.00 – 5.00
5	insufficient data