I have a 30 amp double breaker that is crackling and gets hot. It is for my hot water heater. Can I replace it temporarily with 2 20 amp breakers until I can get a new one in the morning.

The old breaker definitely needs replaced

And I think it would be best to turn off power

Until you get the proper sized breaker

You may have to rough it one night

Like people who go camping do

The 20 amp breaker would have sufficed for the night, if it tripped, no harm done.

Be sure to check the tabs the breaker plugs onto in the panel for any damage also.