I think it needs to be closer to 40 for them to go on the reefs to spawn. They stage outside of Huron before moving back west. You can definitely have luck in colder water just like ice fishing but trying to hit them spawning in 35 degree water is hard. And yea, the water was close to spawning temp and then dropped back down. I think that shocked them back to more of a staging position. It's mid/late March and I'd say any nice day now they'll be moving on to the reefs. Just my thoughts.