In addition to the physics of fuel burning...

Your engine bay gets extremely warm in 90 degree plus weather. This causes the fuel to boil in the line between the pump and carbs. This can force the fuel past your needle valves in the float bowls and flood the engine or cause a rich condition. It also leads to "vapor lock."
Recently, I pulled the fuel filter to change it after a run in the heat and was nearly bathed by the major jet of fuel spurting out! Many quick steps back until it all evaporated and blew away! I felt darn lucky I wasn't a smoker.

This isn't a big issue when you are cruising, but idle for awhile or shut down and restart "hot" and the problems manifest in poor running or failure to start.

I have tried insulating the line but there is very little to be done in that regard, short of running it through a "cool can." My next trick will be to put in a by-pass style fuel pressure regulator with a return line to a custom fitting on the tank... That may only increase the vapor lock but we'll see.

--
Mike!