State Precipitation & Temperature Update for Arizona

Conditions through February 2012

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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.

AzClimDivs 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. The percentiles have shifted to reflect the percentile categories used in the National Drought Monitor. Current update is 4/10/2012. The data are preliminary.

Precipitation Percentiles by Watershed (through February 2012)

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Temperature Percentiles by Climate Division (through February 2012)

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SHORT TERM CONDITIONS: 1-6 MONTHS

February was near average or slightly drier than average for most watersheds, except central Arizona, which was much drier than average. The Verde, Bill Williams, and Agua Fria watersheds were at or below the 15^th percentile, while seven watersheds were between the 20^th and 30^th percentile. Fortunately temperatures were only slightly warmer than normal, between the 59^th and 66^th percentiles for all counties except Maricopa and Pinal, which were at the 77^th percentile. The three month precipitation was near average statewide, mostly as a result of December storms. Those storms and cold January conditions kept temperatures near or slightly warmer than average, between the 53^rd and 70^th percentiles in all counties except Mohave, which was at the 77^th percentile. Six month precipitation was also near average or only slightly drier than average for all watersheds. The driest were the Salt, Upper Gila and Lower Colorado, all at the 30^th percentile. Six month temperatures were near or slightly warmer than normal in eleven counties, with only La Paz, Yuma, Maricopa and Pinal counties above the 74^th percentile. The cooler temperatures helped preserve what little snowpack we received at the higher elevations.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	21.43	CD1	63.14
Upper Colorado	35.71	CD2	60.17
Little Colorado	28.57	CD3	59.32
Verde	14.29	CD4	64.41
Bill Williams	14.29	CD5	62.71
Agua Fria	14.29	CD6	77.12
Lower Gila	21.43	CD7	65.68
Salt	19.05
Lower Colorado	21.43
Upper Gila	23.81
Santa Cruz	28.57
San Pedro	26.19
Willcox Playa	34.15
San Simon	30.95
White Water Draw	35.71

FEBRUARY 2012: 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	30.00	CD1	77.12
Upper Colorado	34.15	CD2	58.90
Little Colorado	55.00	CD3	53.81
Verde	35.00	CD4	55.93
Bill Williams	43.90	CD5	62.71
Agua Fria	41.46	CD6	70.34
Lower Gila	29.27	CD7	64.83
Salt	41.46
Lower Colorado	21.95
Upper Gila	53.66
Santa Cruz	46.34
San Pedro	43.59
Willcox Playa	47.50
San Simon	46.34
White Water Draw	52.50

DECEMBER 2011 - FEBRUARY 2012 (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	34.21	CD1	69.49
Upper Colorado	36.59	CD2	47.46
Little Colorado	52.50	CD3	57.20
Verde	35.00	CD4	64.41
Bill Williams	34.15	CD5	77.97
Agua Fria	31.71	CD6	85.59
Lower Gila	34.15	CD7	74.58
Salt	29.27
Lower Colorado	29.27
Upper Gila	29.27
Santa Cruz	39.02
San Pedro	33.33
Willcox Playa	40.00
San Simon	41.46
White Water Draw	45.00

SEPTEMBER 2011 – FEBRUARY 2012 (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 still the driest short-term period, with only the upper Colorado, Little Colorado, and White Water Draw watersheds near normal. Nine watersheds are below the 20^th percentile and three are below the 10^th percentile. Temperatures were near average in Mohave County, and much warmer than normal in southern Arizona. The much warmer than normal conditions in southern Arizona are a result of the dry, hot monsoon last summer, and a warm fall.

The 24-month period is now the driest long-term interval with 12 watersheds at or below the 20^th percentile, and five of those at or below the 10^th percentile. The Agua Fria, Santa Cruz, and San Simon are at the 2.5 percentile. Temperatures for the last 2 years have been much warmer than average in the southern half of the state and only slightly warmer than average in the northern counties.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	10.26	CD1	58.97
Upper Colorado	36.59	CD2	61.54
Little Colorado	36.59	CD3	77.78
Verde	12.20	CD4	83.76
Bill Williams	12.20	CD5	81.20
Agua Fria	7.32	CD6	90.60
Lower Gila	21.95	CD7	94.02
Salt	17.07
Lower Colorado	14.63
Upper Gila	19.51
Santa Cruz	9.76
San Pedro	24.39
Willcox Playa	22.50
San Simon	9.76
White Water Draw	32.50

MARCH 2011 - FEBRUARY 2012 (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	21.05	CD1	63.79
Upper Colorado	52.50	CD2	57.76
Little Colorado	55.00	CD3	75.00
Verde	17.50	CD4	78.45
Bill Williams	10.00	CD5	78.02
Agua Fria	2.50	CD6	82.76
Lower Gila	12.50	CD7	85.34
Salt	17.50
Lower Colorado	20.00
Upper Gila	7.50
Santa Cruz	2.50
San Pedro	12.50
Willcox Playa	12.50
San Simon	2.50
White Water Draw	17.50

MARCH 2010 - FEBRUARY 2012 (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 no longer the driest long-term interval, as it has three watersheds with near average precipitation, and four others only slightly drier than average. However, the situation is not good, as four watersheds are between the 10^th and 16^th percentiles and four others are below the 8^th percentile. We still have long-term drought issues where aquifers have not been sufficiently recharged. Temperatures for the three year period are not as high as they have been in the past, but the southern half of the state is still much warmer than normal. The warmest counties are between the 90^th and 93^rd percentiles.

The 48-month period is also quite dry with the upper Colorado, Salt, and lower Gila near average. The Little Colorado and lower Colorado are only slightly drier than average, but five watersheds are below the 6^th percentile. The dry watersheds are in both southern and central Arizona. The 48 month period remains the warmest long term period, with Maricopa and Pinal counties above the 97^th percentile. Ten counties in southern Arizona are above the 79^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	21.62	CD1	66.09
Upper Colorado	51.28	CD2	59.57
Little Colorado	46.15	CD3	78.26
Verde	10.26	CD4	77.39
Bill Williams	7.69	CD5	81.74
Agua Fria	5.13	CD6	92.17
Lower Gila	35.90	CD7	90.43
Salt	23.08
Lower Colorado	28.21
Upper Gila	10.26
Santa Cruz	2.56
San Pedro	15.38
Willcox Playa	20.51
San Simon	2.56
White Water Draw	15.38

MARCH 2009 - FEBRUARY 2012 (36-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	65.79
Upper Colorado	44.74	CD2	72.81
Little Colorado	28.95	CD3	79.82
Verde	5.26	CD4	64.47
Bill Williams	10.53	CD5	84.21
Agua Fria	2.63	CD6	97.37
Lower Gila	52.63	CD7	86.84
Salt	36.84
Lower Colorado	26.32
Upper Gila	18.42
Santa Cruz	2.63
San Pedro	10.53
Willcox Playa	15.79
San Simon	2.63
White Water Draw	18.42

MARCH 2008- FEBRUARY 2012 (48-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

March 2012 Arizona Drought Update (based on precipitation data through February 2012)

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 precipitation was near average statewide, mostly as a result of December storms. Those storms and cold January conditions kept temperatures near or slightly warmer than average, between the 53^rd and 70^th percentiles in all counties except Mohave, which was at the 77^th percentile.

The 6-month period precipitation was also near average or only slightly drier than average for all watersheds. The driest were the Salt, Upper Gila and Lower Colorado, all at the 30^th percentile. Six month temperatures were near or slightly warmer than normal in eleven counties, with only La Paz, Yuma, Maricopa and Pinal counties above the 74^th percentile. The cooler temperatures helped preserve what little snowpack we received at the higher elevations.