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Climate of the Upper Colorado River Planning Area

The Upper Colorado River Planning Area has a distinctive bi-modal precipitation pattern found in other regions of the State, though this planning area is overall relatively dry.  Summer precipitation peaks in August during the summer monsoon thunderstorm season.  There is a secondary peak during December, and the May-June period is typically extremely dry.  The area receives 58% of its precipitation on average during winter months (November-April), and higher elevations (e.g. Hualapai and Cerbat Mountains) typically receive some snow.  From 1930-2002, average precipitation in Kingman was 10.2 inches, with 32% coming in July, August, and September (Figure 4.0-6).  Average precipitation along the Colorado River is much lower, with an average of 4.9 inches recorded at Lake Havasu City from 1967-1991 and an average of 2.9 inches from 1991 to 2003.  Kingman is the only location in the planning area with long-term weather records.

Figure 4.0-6 Average Monthly Precipitation and Temperature in Kingman, Arizona, 1930-2002

Figure 4.0-6

Data are from selected Western Regional Climate Center cooperative weather observation stations.

( Figure author: CLIMAS.

Precipitation patterns in Kingman are generally representative of much of the planning area.  As in other areas of Arizona, precipitation is extremely variable, both spatially and temporally.  For example, in 1988 Kingman recorded 13.3 inches of precipitation; in 1989 the total was 4.3 inches.  This variability also may be observed on longer time scales.  The 1950s and 1960s were relatively dry decades with an average annual precipitation deficit of -0.95 inches, while the 1980s was a relatively wet decade with an average annual precipitation surplus of 1.42 inches (Figure 4.0-7). 

Figure 4.0-7 Average Temperature and Total Precipitation in Kingman, Arizona from 1930-2002

Figure 4.0-7

Horizontal lines are average temperature (61.6 F) and precipitation (14.7 inches), respectively.  Light lines are yearly

values and highlighted lines are 5-year moving average values.  Data are from selected Western Regional Climate

Center Cooperative weather observation stations. Figure author: CLIMAS

Winter precipitation records dating to 1000 A.D. have been reconstructed from tree rings.  They show extended periods of above- and below- average precipitation in every century in the area defined by the National Oceanic and Atmospheric Administration (NOAA) as Climate Division 1, which corresponds to Mohave County (Figure 4.0-8).  A climate division is a region within a state that is generally climatically homogeneous.  Arizona has been divided into 7 climate divisions. In addition to Climate Division 1, the western part of Climate Division 3 (Yavapai County) and small portions of climate divisions 2 (Coconino, Navajo and Apache counties) and 5 (La Paz  and Yuma counties) are located in the planning area.

Figure 4.0-8 Arizona NOAA climate division 1 (Mohave County) winter (November-April) precipitation departures from average, 1000-1988, reconstructed from tree rings

Figure 4.0-8

Data are presented as a 20-year moving average to show variability on decadal time scales. Values

shown for each year are centered on a 20 year period. The average winter precipitation for 1000-1988 is 4.9 inches.

Data: Fenbiao Ni, University of Arizona Laboratory of Tree-Ring Research and CLIMAS. Figure author: CLIMAS.

Precipitation variability on time scales of 10-30 years likely is related to shifts in Pacific Ocean circulation patterns, such as the El Niño Southern Oscillation (ENSO) or the Pacific Decadal Oscillation (PDO).  The ENSO phases, El Niño and La Niña, impact precipitation in the planning area.  During El Niño episodes, there are greater chances for above-average winter precipitation as storm tracks across North America shift farther south than normal.  La Niña conditions usually are associated with below-average winter precipitation.

Annual average temperature in Kingman is 61.9° F, compared to the statewide average of 59.9° F.  The annual average temperature in Bullhead City for the period 1977 to 2006 was 74.2°F.  As in other planning areas, temperatures have been increasing the past several decades (Figure 4.0-7), consistent with global temperature trends.  Some warming may be attributed to changes in land-cover resulting from population growth.


For additional information on climate in individual basins in the Upper Colorado River Planning Area see Climate on the menu to the right.


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