As we found out this year, it can rain enough in Phoenix to cause widespread flooding -- enough to put cars underwater on the Interstate.
According to the National Weather Service, "A microburst is a downdraft (sinking air) in a thunderstorm that is less than 2.5 miles in scale. Some microbursts can pose a threat to life and property, but all microbursts pose a significant threat to aviation. Although microbursts are not as widely recognized as tornadoes, they can cause comparable, and in some cases, worse damage than some tornadoes produce. In fact, wind speeds as high as 150 mph are possible in extreme microburst cases."
These hit the Phoenix area every so often.