How do I prevent hail from destructing my veggie garden?

It is a force of nature you can't predict. The only way would be to put up some kind of posts that you can attach a cover to for times that hail is predicted. We have had hail predicted more than once a day, almost every day, for the past 5 days with all the waves of rain and thunderstorms that have been coming through the last 5 days. We saw hail twice, very small for about two minutes each that wouldn't harm a fly, much less your garden. Having a cover above all plants would be the only solution I can think of, perhaps a tarp may be thick enough. The biggest problem is that the garden will not get the rainfall and the rainfall could collect on the tarp unless you make sure it is taut and has a post in the middle of the garden to keep the center elevated to allow the rain to run off. I don't know if landscape fabric would hold up if you have larger hail to allow the rain to go through it. Hope this helps get the brain juices flowing to get an idea of what you want to do.

I deal with this a lot in Colorado. If your plants are still small enough, cover them with an ice cream bucket or 5 gallon bucket. Once they are larger - like a pumpkin plant - you can try to cover them with towels/blankets to the best of your ability.

You can cover the garden with tarps, if you know ahead of time it's going to hail. If it's a re-occuring problem, build a box of wood and chicken wire to keep over your different plants. This would help them be covered without damage to the plants - and you can put a tarp over without flattening the plants.