As the weather becomes more inviting, we feel the urge to get off the boring treadmill and move outdoors. This is wonderful "rite of passage", but take time transition back into the groove of the road.
You may want to ease back into outdoor running one to two times a week at first. It can still be a little cold out there, particularly in the early morning, so give your body a couple of weeks to adjust.
Check to make sure whether or not you need new shoes prior to moving back outdoors. Unless you're headed to a track, chances are your outdoor running surface will be a lot harsher than your treadmill surface. Make sure you're feet are properly equipped.
Speaking of tracks, you may want to try running on the softer surface of the track prior to venturing out on the harder surfaces.