The plants growing in your woods are a better soil thermometer than any model on this site, because they are standing in the exact ground you are about to hunt and responding to the exact same trigger.
Loading station observations.
A model built from a weather station forty miles away is describing a region. A trillium at your feet is describing the square metre you are standing on. Spring ephemerals break dormancy on soil temperature and accumulated warmth, which is the same signal that drives morel fruiting, so their timing tracks the thing you actually care about.
This is not folklore dressed up. It is the same logic professional phenology networks use, and it is the reason experienced hunters glance at the ground cover before deciding whether a spot is worth walking.
The most quoted indicator in Michigan. When trillium are blooming across a piece of woods, the soil there has warmed into the range. Trillium are also a useful reminder about restraint: picking them can kill the plant, so look and leave them.
Ferns pushing up and starting to straighten out of their coil is the second classic signal. Tightly curled means early, fully unfurled means you are into it.
Not a woods plant, but it is in half the yards in Michigan and everybody notices it. Lilac coming into bloom is a rough regional marker that spring has arrived properly rather than teased.
This site tells you when to look. It will never tell you what is safe to eat. False morels grow in the same woods at the same time of year and people are hospitalised by them in Michigan every spring. Some contain gyromitrin, which can cause severe poisoning and has killed people.
Learn identification in person, from someone qualified, before you eat a single mushroom. Michigan runs a certified wild mushroom expert programme, and the Michigan Mushroom Hunters Club holds forays where you can learn from people who know. If you are not certain, do not eat it. Certainty means certain, not fairly sure. What false morels look like.
The two work at different scales and the combination is stronger than either.
If tracking that kind of thing appeals to you, the Saginaw Bay phenology dashboard follows the same class of seasonal signal through the whole year rather than just the spring.