CSL - Can you use a swim spa during the winter?

You can absolutely use a swim spa in the winter or any season. One of the pros of a swim spa is that is can be used year-round as long as you have the right insultation type, a swim spa cover when it not in use, and the proper heater than can heat the water to your desired temperature in your area. This will come down to the kWh (kilowatt-hour) that the heater produces. The higher the kWh, the greater its ability to keep the water temperature warm despite cold weather.