You should always use OEM glass to insure your safety. Make sure it is written and covers water and air leaks. It should be for at least a year. Many shops offer a lifetime warranty. Also if there is a problem with the windshield not seating or sealing properly, the shop should take care of it.
All Reputable shops stand behind their work.
Don't be shy about asking for a warranty. Your safety and comfort are worth it. No reputable company will a windshield during poor weather conditions. You should avoid having your windshield replaced outside when the weather is bad. Reputable companies will do that anyway since their reputation is on the line.