A powerful new computer which gives more accurate and detailed forecasts is being used at the Met Office in Devon.
The computer is about the size of two football pitches and can make about 750 trillion calculations a second - equivalent to 100,000 PCs.
It is 30 times more powerful than the one installed by the Met Office, in 2003, ahead of its move to the new headquarters in Exeter.
The system is expected to be fully up and running by August.
Chief technology officer Steve Foreman said it was probably the second most powerful computer in the UK and would be in the top 20 in the world.
In order to give a more accurate forecast, the new computer breaks down the atmosphere into grid boxes of about 1.5km - considerably smaller than the previous computer's boxes of 4km.
"We should get a much better idea of where showers will occur and also the areas where there will be no showers, so people can plan their day," chief forecaster Nick Grahame told BBC News.
"Another important thing is these models should give us a better representation of severe storms and sever weather.
The system will also be used for research on climate change and its impacts on society and the economy.