Forcing the Brits to not know about the weather is a vicious attack akin to killing puppies and children and sending the bodies to the Queen on her birthday. Needless to say there would be pressures for an immediate nuclear strike on Syria. The attack was carried out by the "Syrian Electronic Army", a group of pro-Assad hackers and online activists that has already disrupted the Facebook page of Barack Obama.
Other people it has hacked include the Human Rights Watch and the Twitter account of French news service France 24. After all when you are accused of using chemical weapons against your own people it is always a good idea to get world support by hacking them.
The BBC Weather Twitter feed began posting unusual messages in the early afternoon, ranging from offensive to humorous and often making reference to Syria and Middle Eastern politics.