I couldn't find ice-in data on Lake Vermilion but mid-November is typical. Usually occurs during firearms deer hunting but has occurred at the beginning and end of November. May occasionally deviate outside of November. Would be interesting to see the data.
Our group has been going up early to mid October for years but have also done September. You will likely catch more fish in October but weather is hit or miss. Example is this year...we were up this past weekend and it was miserable. Snowed every day and highs in mid 30s. Last year we were up the same weekend and fished in sweatshirts. That’s the gamble you have to take with October. We just don’t have the choice for now.
Edit: FWIW I’ve had plenty of bad/windy days in September too. But the bad in October are worse.