Solar panels are, as a matter of fact, very vulnerable during hailstorms. The hail will smash the panels and destroy the electrical system. If the solar panels have a grill protecting them, they might survive the storm.
The best way to protect them from hail damage is to get some 1/4" to 1/2" thick Lexan plexiglass and install them over the panels , The thicker the plexiglass , The better the protection , Lexan is the toughest plexiglass and will protect the panels , Even though pricey , But is worth it , Cut the plexiglass so that about an inch extends beyond the panels , Then attach narrow strips of pressure treated wood to the perimeter of the plexiglass using stainless steel sheet metal screws , The wood strips must go around the outer part of the panels , This keeps the plexiglass from moving around and then , Secure them in place using bungee cords , Going around the front and back of the panels and hook the two ends together , WARNING ! , , , NEVER drill into any part of the panels as you will damage them Later on , If the plexiglass becomes dull & dingy , You can use automotive headlight lens restorer to restore it's clarity