Under the Köppen climate classification, Salt Lake City is either a humid subtropical climate (Cfa) or a humid continental climate (Dfa/Dsa) depending on which variant of the system is used, though it borders on a Mediterranean climate (Csa) as summers are dry and hot and winters are wet and cold (though not typically severe).
The primary source of precipitation in Salt Lake City is massive storms that move in from the Pacific Ocean along the jet stream from October to May. In mid-to-late summer, when the jet stream retreats far to the north, precipitation mainly comes from afternoon thunderstorms caused by monsoon moisture moving up from the Gulf of California. Although rainfall can be heavy, these storms are usually scattered in coverage and rarely severe. However, downtown was hit by an F2 tornado on August 11, 1999, killing 1 person, injuring 60, and causing $170 million in damage. The remnants of tropical cyclones from the East Pacific can rarely reach the city during Fall. The remnants of Hurricane Olivia helped bring the record monthly precipitation of 7.04 inches (179 mm) in September 1982. 1983 was the wettest year on record, with 24.26 inches (616 mm), while 1979 was the driest, when 8.70 inches (221 mm) were recorded. Spring snowmelt from the surrounding mountains can cause localized stream flooding during late spring and early summer, the worst examples being in 1952 and especially 1983, when City Creek burst its banks, (Creek-bed scouring in Memory Grove, caused by high spring run-off in City Creek, filled much of the submerged waterway running westward under North Temple Street towards the Jordan River) forcing city engineers to convert several downtown streets into waterways.