▁the ▁coast al ▁bas in ▁is ▁generally ▁too ▁stable ▁and ▁dry , ▁especially ▁during ▁summer , ▁to ▁allow ▁the ▁strong ▁vertical ▁development ▁necessary ▁for ▁m ature ▁cum ul on im bus ▁clouds . ▁Full , ▁m ature ▁th under st orm s ▁can ▁develop ▁in ▁the ▁surrounding ▁desert s ▁and ▁mountains ▁during ▁the ▁summer ▁North ▁American ▁Mon so on , ▁but ▁rarely ▁over ▁the ▁Los ▁Angeles ▁metropol itan ▁region ▁and ▁coast al ▁bas in ▁but ▁the ▁mo ist ure ▁is ▁coming ▁off ▁on ▁G ulf ▁of ▁Mexico ▁and ▁G ulf ▁of ▁California . ▁This ▁atmos pher ic ▁stability ▁is ▁largely ▁due ▁to ▁the ▁cool ▁and ▁persistent ▁marine ▁layer , ▁which ▁is ▁fue led ▁by ▁the ▁constant ▁infl ux ▁of ▁cold ▁Pacific ▁water ▁via ▁the ▁California ▁Current . ▁Summer ▁th under st orm s ▁that ▁do ▁manage ▁to ▁form ▁on ▁the ▁coast al ▁bas in ▁are ▁typically ▁associated ▁with ▁the ▁North ▁American ▁Mon so on ▁and / or ▁tropical ▁cycl ones , ▁or ▁down bur st ▁wind s , ▁which ▁can ▁bring ▁enough ▁tropical ▁heat ▁and ▁mo ist ure ▁to ▁overcome ▁the ▁cool ▁marine ▁layer , ▁dest abil izing ▁the ▁atmosphere . ▁ ▁Though ▁still ▁relatively ▁rare , ▁th under st orm s ▁most ▁often ▁occur ▁during ▁warm ▁sou ther ly - flow ▁winter ▁rain ▁storm s . ▁These ▁warm ▁storm s ▁are ▁different ▁from ▁the ▁typical ▁north w ester ly ▁cold ▁front s ▁that ▁bring ▁most ▁of ▁the ▁region ' s ▁winter ▁precip itation . ▁At mos pher ic ▁inst ability ▁caused ▁by