During my first week at Thurloxton Manor the weather was quite hot and the owners invited me to swim in the outdoor pool they have at the bottom of the garden. The thought was infinitely more lovely than the deed, due to temperature of the water. It took me a very long time to immerse myself, and I couldn't swim for long because my feet went numb. I'm told the water gets hot by August if there's been a warm summer.
By contrast I went swimming yesterday in Louisiana. The pool water was as warm as a pleasant bath. I'm planning on going every day. However It's raining today, and I learned from living in North Carolina, that it's dangerous to swim outdoors in the rain in case a lightning bolt hit the water and electrocutes you. I swam in the rain in an outside pool in Britain when I was a child. It was fun. British rain is rarely accompanied by thunder and lightning - only if it's been particularly hot weather.