Carburetor icing between 38 and 40 degree temp in high humidity is common. Air rushing through the carb pulls heat out of the metal. When humid air comes in contact with the metal, it condenses and forms ice, both inside and outside of the carb. Most people don't drive far enough to notice the ice on the inside. Back when these vehicles were all we had, it was common for them to lose power and smoke black like the choke was pulled out after about a half hour of driving. This was caused by the venturi becoming smaller because of the ice. A common fix was to take a leak on the carb to warm it up.
