The last couple of days really have felt like spring has already sprung. You heard me say more than once that you should seed spring wheat, barley, oats early and as soon as the ground is ready. But can you actually be too early? The simplest answer is 'probably not', as long as the seed can get through the imbibition phase and the little germ starts actively growing. Once the radicle and shoot appear, the young seedling can handle some freezing temperatures even if the coleoptile hasn't reached the soil surface yet. So if you can prepare a good seedbed and the immediate forecast is warm enough that you can accumulate about 150 to 180 growing degree days in the 4 to 5 days after seeding, and before freezing temperatures return, you can probably seed your first small grains. Even if we're only the middle of March and winter weather might return later this month or in April.
Source : umn.edu