I got this info from the UMich website:
https://careercenter.umich.edu/content/find-job-or-internship
https://lsa.umich.edu/opportunityhub/students/internships1.html
The acceptance rate is 19% for OOS.
Chicago is about 3 hours away, Detroit is about 35-40 minutes from Ann Arbor, but UMich offers internship opportunities all over the country.
As for the weather, Ann Arbor is cold during the winter. It can be 40 degrees one day, then 10 degress the next. And it can be grey for days. The Winter semester (what other universities call Spring semester) ends late April, so you can be back in sunny SoCal before the end of April. :))
On the bright side, the town is relatively small and cute. Very walkable. And the campus is compact IMO, not sprawling, unless you’re placed in the dorms on North campus.