There are complicated answers to this question. A lot of it can depend on what other modifications you have done to your car. The Beetle was designed to run in all sorts of climatic conditions as long as the carefully designed cooling system remains as it came from the factory. Some of the "improvements" done by owners actually compromise the efficient original design. The worst of these improvements is the deliberate removal of the engine shrouds and tin work. The engine compartment is a closed system which brings cooling air through the engine cover louvres and directs it down over the fins on the cylinders and the heads and out the bottom of the engine at road level. If air comes from other sources this system can be thwarted and overheating ensues. Things like the engine cover seal and the seals back at the firewall and around the edges of the engine tin all come into play. If they are intact - good. If they are ripped, missing or have gone hard with the heat they will not do their job and your engine will run hot. It should not be necessary to have the offset opening in the engine compartment lid either, even in hot climates. Make sure that all of your tin is in place, your oil cooler is operating right, your thermostat is opening the louvres in the fan, your generator/alternator belt is correctly tightened, your timing is set correctly and you should not have overheating issues.
I'd rather have a partial bottle in front of me than a partial frontal lobotomy.