It really is as simple as that, just like Greg G just posted.
When it's a 19-and-a-half mph day, and you want to improve your chances as much as possible, you need to use a longer launch guidance system and a more rigid, stiff launch guide. This usually means going up in size to 1/4 inch diameter launch rods (or bigger) and using a 4, 5, or 6 foot length. (Yeah, you need 1/4 inch launch lugs on your rocket too.) You can find steel round rod at a lot of local hardware stores, in the section with angle stock, bar stock, and all-thread.
Even better, a launch rail (properly built) is a rock-solid system. These can be used even with model rockets, although most guys probably use them for mid-power motors and larger. The rail (and the rest of the launcher) needs to be well built, but you can find lots of designs for sale and more designs posted on the web that you can build yourself. With a 6 or 8 foot long guide rail, your rockets will get a much better chance to build up safe flying speed on a windy day before they leave the end of the rail. You will have to change your launch lugs for rail buttons, but that's usually no big deal.
One other option: you might want to look into a tower launcher. You can build one with an old bucket, a sack of concrete, and three straight pieces of electrical conduit (metal pipe). You won't need a launch lug, and if you pot the conduit into the bucket with concrete (permanently) it won't be adjustable for different sized rocket diameters. But then, if you want to get fancy, there are plans available for adjustable towers.
I'm sure these guys can pitch in with a ton of suggestions for launch hardware.