Weather in March?

Hi everyone!!

So my family and I are doing a two week trip from Australia to Los Angeles/Las Vegas in March, but I am worried the temperature will be completely different from what the weather is predicted to be. Will it be cold and rainy more often or sunny and humid? I obviously will pack for both occassions, but what should I favour more?

Thank you so much!!

(Also please add any fun events/places that aren't common to add to our plan on days where we aren't doing much. Thanks!!)