Annual precipitation for the Salt Lake Valley is around 15 inches (380mm), usually with more on the east side and less on the west side, as most storms come from the Pacific Ocean and the west side is in the rain shadow of the Oquirrh Mountains. Up to 19 inches (500mm) is received on the east benches. Most of this precipitation is received in spring. The summer is dry, with the majority of precipitation arriving from the monsoon that rises from the south. Short, localized, and often dry thunderstorms are usually associated with the monsoon. However, some can be very intense. These storms can cause contrasting emergencies of flash floods and wildfires (due to dry lightning and powerful winds). Precipitation is heaviest in late fall/early winter and in spring, while early summer is the driest season.