I had the opposite problem of you guys. Sonya had finished all her shedding out at the end of Febuary, and I live in Canada! She did have a blanket on from the end of November until March tho, and she was preggo, so her body probably thought it was time to shed because she was so warm.
The TB I am exercising this year still has all his guard hair and smaller hairs. Its crazy. We I use the shedding blade on him he doesnt even shed. It might be time to break out the clippers soon because he is starting to sweat on warm days when he is just standing in the cross-ties getting groomed.