Timing wise... here in southern Middle TN... I find them in early to mid April but the exact timing on that will vary depending on how early or late spring is for the current year, and also moisture conditions.
Going by Tree blooms...
When red buds are in full bloom, and dog woods blooms are just starting to open.. that seems to be the sweet spot for me.
When red bud blooms first start, until dogwoods are in full bloom - you need to be looking.
Some morels come up earlier (blacks)... and some come up later (yellows).
Read the stickie at the top of the mushroom section. Big help. Looks like soil temp is close here in Ohio, according to the USDA site. Today it is 51°F at 2\" in Madison county, and 50° at 8\". This weekend is looking good.