Timing is criticial in finding morels. They come up about six weeks after the ground thaws. It might be eight weeks, if dry weather slows down their growth. This means early April in Missouri, late April in Iowa and middle of May in northern Michigan. Experienced morel stalkers check an environment several times starting early and after every rain.
Morels usually come up after a rain.
The day after a rain is the best time to look for them. They will still be in good shape for 3-5 days, if someone else doesn't get to them. In about a week, they start to break down, and bacteria grow on them, which will make a person sick. So don't eat morels which are old and starting to break down. Sometimes, morels will come up in flushes each time a rain occurs.