Local News stations are saying 50-53F with a 5-15mph E/NE wind. Rain showers will be rolling in during the day. Early forecasts suggest that the rain might hold off until the afternoon. One reporter went as far as to say it "should" hold off later in the day. It's too early to say though. I'll try to update this post if/when things change in the next few days.
Weather.com, accuweather can be vague. Hope this helps.
Those of you who ran Boston in the recent storm of '06(or something). Were there still a lot of spectators? I'm counting on them to get me through and I hope the bad weather doesn't keep them away.