That is the one thing I always worry about with planting too soon. You get one little pop-up shower to trigger germination and then it returns to being the Sahara for weeks on end. That's why I wait until closer to Labor day. We tend to get more regular rains come fall vs July and Aug. Except for this year....we have had a very wet July thus far here. Still doesn't mean it won't be drier than a popcorn fart here come Aug.