While fruit flies can't actively develop in the cold, they can survive in a dormant state.
When temperatures drop below 53°F (11.7°C), fruit fly development ceases entirely. However, adult fruit flies possess a survival mechanism known as "overwintering." This allows them to endure frigid conditions, essentially going into a dormant state. When favorable conditions return, they can then reproduce and start a new generation.
In summary, fruit flies can "overwinter" and thus survive the cold, even though they cannot develop at temperatures below 53°F.
