I seeded on top of snow last year (mainly perennial rye) (in a flower pot outside). My photos are on here somewhere...I think.
Found it...Seed sprouted April 15 after 72 days.
Spring-seeded grass, was a quarter-inch tall after 18 days on April 25th. The soil temp on that date was 52.
Soaking the seed 24 hours before it was planted in spring caused it to arise after only nine days.