In the past two weeks we have seen a rash of electrical panels all failing because of corrosion caused by moisture. These panels probably had moisture getting in for some time and the heavy rains of the past two weeks finished them off.
The crazy thing is that $3 worth of silicone sealant would have prevented the problems. Just seal around the top and sides of your panel (leave the bottom open so that any water can still drain out if it should manage to get in).
Even if there never was any silicone around your panel — or if there once was but now it's old and cracked — you can go a long way toward preventing a costly service replacement by getting some new sealant on there now.