Per Sam Amick, retweeting the Heat Owner Micky Arison:

Ray Allen to Miami, apparently RT @MickyArison: Its 2:30am in London and I was just woken up with great news.Welcome to the family #20!!

— Sam Amick (@sam_amick) July 7, 2012

Update: It's done.

The agent for Ray Allen, Jim Tanner, confirms that he has agreed to join the Miami Heat.

— Sam Amick (@sam_amick) July 7, 2012

Update: Woj explains some of Ray's motivation:

The deterioration of Ray Allen's relationship with Rajon Rondo played a significant factor in his leaving for Miami, several sources tell Y!

— Adrian Wojnarowski (@WojYahooNBA) July 7, 2012

As Y! had reported, Allen was angry w/ near-trade to Memphis at deadline. Too much acrimony to get past. Off to Miami for less money.

— Adrian Wojnarowski (@WojYahooNBA) July 7, 2012

There's going to be a lot of negative reaction to this. I hope fans can focus on the five seasons of stellar basketball and the championship Ray helped bring us. He apparently wanted stability and a larger role on a championship caliber team, and Ray must feel like he got that. I can't necessarily wish Ray the best, but I appreciate what he did for us, and I respect his decision.

Details on Ray's reported contract demands, after the jump...

Allen Chooses Heat - BostonHerald.com - Celtics Insider Blog

Allen, tired of being offered as trade bait by Danny Ainge in each of the last two years, was also being offered trade security by the Celtics, either in the form of a trade kicker or a no trade clause.

But according to a league source, Allen’s request from the Celtics went beyond the pale - reportedly a demand for a three-year, $27 million contract. The Celtics, according to the source, were in the process of attempting to talk Allen down from $9 million to $6 million per year.

If those were Ray's demands to stay in Boston, no wonder Danny let him go.