No I'm not promoting obesity. I'm referring to outdoor presentations. If you are ever forced (I say "forced" because you should try to avoid outdoor presentations at all costs) to do an outdoor presentation, then make sure you have several different kinds of weights handy to help control your presentation.
You might need a sand bag or dumbell to hold down the easel of your flipchart. How about taping some heavy coins to the bottom of the sheets and clamping the edges to keep the breeze from lifting up the pages?
Paperweights, or in a pinch, plain old rocks are great for holding down papers you have on a table on stage.
What else do you commonly have with you on stage that could blow around in a breeze? Make sure it's secured.
Ties and scarves that look gorgeous in a no wind hotel room look terrible and distracting when flapping in the wind.
Keep your weight up and you'll make the best of a windy situation.