Living in South Florida we sometimes (often) get torrential downpours! Being used to it, if traffic allows, I tend toward maintaining or minimally reducing my speed. In one instance I was moving along, looked in my mirror and realized my TT was tracking to the right being pushed by the side wind. Tapped the trailer brakes manually and realized the trailer was hydro planing. I slowly decelerated, not using the brakes, and I could feel the drag when the trailer tires made contact with the pavement. As for speed.... Yeah as road conditions, visibility, and traffic allow.