The below links and Apps, will help to keep you a head of the game.
I use 3 different weather reports and I am guided by the 2 which show the same information. Ihave find these was very trustworthy.
(1) BBC Weather (http://www.bbc.co.uk/weather/2637487)
The BBC also have a rain rader, which keeps track of where it has rained. This is not a prediction, but is real time and I find this a great help.
Rain Radar (http://www.bbc.co.uk/weather/2637487)
(2) The Met Office (http://www.metoffice.gov.uk/public/weather/forecast/gcp185f25?tab=fiveDay)
The Met office also have a rain radar, which keeps track of where it has rained. Again this is real time and I have also found this a great help.
This you can zoom in and out of.
The Enviroment Agency has a great website, which allows you to look up the river levels on most UK river’s. ( http://apps.environment-agency.gov.uk/river-and-sea-levels/120717.aspx?stationId=3314)
Mobile Phone Apps
I also have the Met Office weather forecast on my mobile phone.
All these can give you a indication of wind/rain/pressure and many other things which will help you get the edge to catch more fish!
I am not one for the phases of the Moon, as I only get a small opportunity to go fishing each week (and I have to go). However, I do belive that the above makes a big difference to which part of the lake you should head for.
Hope this has helpped.