A:Answer When considering using the Intex - Greywood Deluxe Spa during the winter, you must consider the following; The spa can be installed indoor or outdoor, however if installed and left outside, make sure the temperature is not lower than 39°F (4°C) . The water provided inside of the spa must be higher than 39°F (4°C), so the water inside of the circulation system will not freeze. For the heating system, we recommend your ambient temperature is no lower than 50 ºF (10ºC). For more additional information, please contact our Consumer Service Center 1-800-234-6839.