▁ 4 0 ' s ▁and ▁lower ▁ 5 0 ' s ▁F ▁( 8 - 1 2 ▁C ). ▁ ▁Summer ▁ ▁Sum mers ▁are ▁warm ▁to ▁hot , ▁and ▁nearly ▁completely ▁dry . ▁The ▁summer ▁temperature ▁pattern ▁usually ▁begins ▁in ▁late ▁June ▁or ▁early ▁July , ▁and ▁last s ▁through ▁September ▁or ▁October , ▁although ▁it ▁may ▁start ▁as ▁early ▁as ▁ ▁late ▁May . ▁In ▁August , ▁the ▁average ▁high / low ▁at ▁the ▁University ▁of ▁Southern ▁California ▁dow nt own ▁campus ▁are ▁ ▁and ▁. ▁The ▁same ▁figures ▁at ▁the ▁L AX ▁air port , ▁approximately ▁ ▁to ▁the ▁south west ▁and ▁near ▁the ▁ocean , ▁are ▁ ▁and ▁. ▁However , ▁temper atures ▁across ▁the ▁region ▁often ▁exceed ▁ ▁during ▁the ▁summer . ▁This ▁happens ▁when ▁an ▁atmos pher ic ▁high - press ure ▁area ▁becomes ▁dominant ▁over ▁the ▁Great ▁Bas in ▁of ▁Nev ada ▁and ▁Ut ah ▁( a ▁frequent ▁occurrence ), ▁and ▁the ▁resulting ▁off sh ore ▁flow ▁of ▁the ▁atmos pher ic ▁air ▁mass ▁sh uts ▁off ▁the ▁normal ▁coast al ▁sea ▁b ree ze ▁in ▁Los ▁Angeles . ▁July , ▁August ▁and ▁September ▁are ▁the ▁h ott est ▁months , ▁with ▁September ▁holding ▁the ▁all - time ▁record ▁of ▁. ▁Sk ies ▁are ▁nearly ▁constantly ▁sun ny , ▁unless ▁interrupted ▁in ▁late ▁spring ▁and ▁early ▁summer ▁by ▁the ▁June ▁Glo om ▁pattern , ▁which ▁is ▁un predict able ▁year - to - year . ▁The ▁North ▁American ▁Mon so on ▁can ▁bring ▁occas ional