Average last freeze is:
150-year avg: April 24th
1991-2020 avg: April 21st
Dont have an exact stat on last frost, but if you go by frost with temp of 37F or lower, then the avg last frost is:
150-year avg: May 10th
1991-2020 avg: May 7th
Detroit finished 18th least snowy since 1880 with 23.5" (for reference, you are using the mid 1930s, this would be the 15th least since 1935). Definitely a winter to forget, but cant say we werent due for an unusually low snow year. It happens.