March
Although March is the start of Springtime in Michigan, it is usually just pretty windy and muddy. Though in recent years we've had both hot weather and ice storms in March. March is pretty much a toss up for what kind of weather we'll have.
March is usually what you would call a transition month. I know a lot of people are still in winter coats for half of it, but it's'a lot warmer for me. I usually walk around in a pair of gloves because of the wind, but I don't wear a coat usually. I love the colder weather.
May
As the last full month of Spring, you would think that it would be the best of the lot. You will see a lot of people starting gardens, and Mackinaw Island is known for it's lilac festival during that time.
Unfortunately, my great-grandfather always said don't plant your garden until Memorial Day for a reason. There are plenty of times that we will get frost, or frosty temperatures, up to the third week of May at night.
Memorial Day, at the end of May, is considered the start of the summer vacationing time in Michigan. This is a little strange since the Summer doesn't start until June, but a lot of people open their cottages or get out their boats by Memorial Day weekend for vacations.
April
There is a saying that goes like this: "April showers bring May flowers". April you are pretty well guaranteed to get rain and a lot of it in Michigan. In recent years, we have had an ice storm or two, but generally you will see rain.
For the most part, Michigan starts to give warmer temperatures, and many people start airing out their homes or planning their flower and vegetable gardens.