Yes, Virginia! There is wind chill and it can happen...even here. Those aren't gophers making the gardens tremble today. THAT is W-I-N-D! Fortunately nothing like my family in the Midwest is experiencing. For instance on my patio the thermometer reads 34 degrees. My fields and gardens are not as protected so it is usually 5-10 cooler (or warmer in the summer) At http://www.weather.com/ it says that my zip code is currently showing 38 degrees and "it feels like" 30 degrees due to winds of 14-21mph. So I am guessing that "it feels like" close to 25 degrees here in the gardens at Tre Soli. For weather information the pilots use http://www.noaa.gov/ Each of these two sites has it's assets. I use them both when I want a compete picture of what the weather is and has been as well as educated guesses on what it will be. Try them both why don't you. What are the micro climates like where you are growing?
If you are having trouble finding enough things to keep your frost cover on in the wind try rocks, bricks or even bags of fertilizer, and containers of water can work too. Just be sure things are heavy enough not to be tossed in the wind. Your local hardware store, that carries gardening supplies, may also have U-pins that you can insert into the frost cover and push in to the ground. Be sure your frost cover does not touch the foliage, which means that your cover will billow, that's actually looks kind of cool! There needs to be room for the air to circulate so let it billow.