It can be several things. A clogged radiator. Not enough coolant in the radiator. Using water rather than coolant. A blown head gasket. A cracked head. Running against some kind of resistance, such as an engaged emergency brake, a stuck brake caliper, etc. Other things.
it can..rain has NOTHING to do with your radiator or the thermostat
Car overheats, your heat in your car stops working
check the water level, if its okay then you probably need a thermostat
Be sure the thermostat is not installed backwards.
Take your thermostat out and put everything back together, run your car without a thermostat... If your car no longer overheats, replace your thermostat.
Car overheats or can't reached the normal temperature.
Possibly thermostat is slow in opening.
Thermostat regulator is malfunctioning, water pump pulley could be bad, gas bubble in radiator hose.
You will know of your thermostat is going out when your car overheats, then turn on your heater really hot on full blast, then the temp will instantly drop. This is a sign of a thermostat gone bad.
check your fluids it is probably low on antifreeze and if it still does it change your thermostat that should fix the problem
try a radiator cap......or you have a head gasket leak.
thermostat