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Figure 5B. The same area before Parker Dam. Much riparian habitat and several Chemeheuvi Indian villages existed.in areas now under Lake Havasu. Photos from the files of R.D. Ohmart. summer temperatures exceeding 32 oC (90 OF) for an average of 177 days each year, and winter temperatures rarely (average of 14 days each year) below freezing (Table 1). Precipita- tion is low, averaging 5-10 cm (2-4 inches) per year. A short mid- and late-summer "monsoon" season, with moisture primarily from Mexico, con- tributes about one-third of the pre- cipitation. During the rest of the year, brief and irregular storms, mostly originating from the northwest, make up the remainder of the precipi- tation. Very infrequently, a large amount of rain will fall in a short period of time. This results in huge flashfloods with standing water remaining in some areas for several months. Relative humidity is low (usually 25% or less) resulting In higher temperatures and low rainfall. The combined effects of temperatures over 38 oC (100 OF) and high relative humidity (30%+) during the late summer "monsoon" results in an extremely uncomfortable climate with little relief from precipitation. This extreme desert climate makes the lower Colorado River very impor- tant to the region's overall biotic diversity. Its verdant floodplain valleys sharply contrast with the surrounding deserts. However, plant and animal life within the floodplain must survive both extreme heat and periodic flooding. 7