It's fine...it's how snakes are air-shipped...as long as it's thick styro-foam (like food or prey was shipped in).
pbenner beat me to it, was going to tell you the same things...anyone keeping snakes should always have styro-foam boxes or 'ice chests' (enough to hold all their snakes without crowding) in case of emergencies, either from heat or cold. I've had to use them during long power outage (ice storm!) & my snakes stayed warm enough & healthy with just the warmth from jars of hot water (I have a gas hot water heater) that I changed every 8-9 hours. Whether they need protection from cold OR heat, insulation (in styro or coolers) is the way to be safe. Any time I take a snake in a car trip (for a program or to vet) that's how they travel, for safety...to avoid temperature changes. You can often find styro-foam boxes cheaply in thrift stores, btw...if you don't have on hand already.
And btw, when I moved cross-country (3 days worth) that's also how my snakes traveled...& all were fine.