It's a beautiful Patriots day in Boston. The weather is pretty much going to be ideal for the spectators but maybe a tad warm for the runners, who are going to be running into a slight headwind.
Weather.com is reporting that at 10 am (men's race starts at 10 am - women at 9:30) it will be 57 degrees in both Boston and Hopkinton (with a 8-10 mph wind of or the N/NE). At noon, it will be 66 in Hopkinton and 58 in Boston.
TV info is here:
http://www.letsrun.com/news/2016/04/tv-streaming-information-2016-boston-marathon/
The tracking and live leaderboard is here: