Put your slides in before the strong winds hit you. Having slides out gives the wind more surface to pick up and move. Also, if the wind is strong with rain, water will flow in via slides--top, bottom, and sides. In addition, wind can tear slide toppers. I was once caught in a 65 MPH side wind, and could feel it move my rig, so I speak from experience. I put slides in quickly and then buckled myself into the drivers seat because I figured it would be the safest place if it rolled over.
If you have a very light TT or a tent camper or anything with canvas sides, close what you can and take cover in a strong building such as a cement bathroom or shower room. Luckily there were no tent campers that weekend, but several lighter trailers got rotated to they pointed in a different direction. Interesting thing I noticed later was that camp host RVs were cabled to cement pads!!