The ideal temperature range at which to keep your Venus Fly Trap during its 3 or 4 month dormancy period is below 70 degrees Fahrenheit and above freezing (32 degrees Fahrenheit). So, the direct shortest answer is between 32 and 70 degrees Fahrenheit (0 to 13 degrees Celsius) for a night-time low and between 45 and 75 degrees Fahrenheit for a day-time high.
Now, what if your plant gets above 65°F, above 70°F, or even above 80°F? Will this trigger your plant to come out of dormancy prematurely? Not necessarily. Don’t worry too much as long as the plant doesn’t stay at that temperature for an extended period of time (more than a few days). In fact, the length of the photoperiod, the amount of time the plant is receiving light during the day, seems to be driving factor as to when a Venus Fly Trap awakens from its winter sleep over the temperature.