The fact that the weathermen and women make so much play of that rapid growth shows how bracing is the free-market wind blowing through this former branch of the Ministry of Defence. Under relentless government pressure it has been forced to become a thrusting, hard-selling 'next steps agency', semi-detached from Whitehall.
Why else would its new chief executive, Professor Julian Hunt, a physicist, speak about 'the great accuracy of our products' - ie weather forecasts? 'We have very high customer satisfaction,' he said. 'We have a commercial dimension and we make no apology for that fact.'
The Met Office's own polling has shown that most people believe there has been a big increase in forecast accuracy since the low point of October 1987, when the weathermen failed to predict the force of the infamous great storm.
Bernard Herdan, director of commercial services, said: 'The old scepticism has gone - people do believe our forecasts now.'
The Met Office calculates that its 24-hour BBC radio forecasts in the early evening were 84 per cent accurate last year. Its predictions for ice on roads were correct 89 per cent of the time.
The organisation, which has 2,500 staff, has been aggressively hunting for businesses which might need customised weather forecasts. Supermarket chains need to know how hot and sunny summer weeks are likely to be in different British regions, to match local demand for salad vegetables. DIY superstores could be wasting their money advertising lawnmowers on televison when it is likely to be raining hard - better to leave them for a sunny day and concentrate on indoor products like paint.
But the government service faces increasing competition. When ITN renewed its weather forecasting franchise two years ago, more than a dozen rivals threw their hats into the ring - the Met Office won.
The organisation earned just under pounds 14m from its commercial services in the last financial year and pounds 24.6m from the Government's Civil Aviation Authority. But the great bulk of its income still comes from the Ministry of Defence, which expects to shave its contribution by 2 or 3 per cent with each passing year.
Mr Herdan said it was increasingly difficult to find fresh customers in Britain 'because we are not far from a mature market situation'. Inevitably the Met Office is looking to export markets, and is considering teaming up with Continental forecasting agencies to create a pan-European weather intelligence corporation.