Well, you can surely use a wireless fence if it's just drizzling. But if it is pouring rain, we suggest you not to use any kind of electric pet fence. The first reason for this is that rain acts as a barrier to electronic signals. So there are chances that the signals may get hindered due to rain and your pet may receive a shock without any reason. However, this problem increases as you go far towards the boundaries. That it is relatively safe to let the dog be nearby the house. So if you can manage that, you may allow the dog to have some fun in the rain.