President Barack Obama has boarded Air Force One bound for Connecticut to attend a church vigil and to meet families of victims of the school shooting in Newtown.
He will also talk to members of the emergency services.
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Temperatures will reach around 28 Celsius (82F) at their highest.
A minute's silence will be observed at 11am on Thursday in remembrance of those who lost their lives in the Manchester Arena attack.
New research has found those who consumed two cups had a 35% reduced risk, and for those who drank five cups, the risk halved.