Nasa experts say eclipse watchers in Esfahan in Iran will have more than a 90% chance of a clear view, while those in Cornwall in south west England have only a 45% chance of seeing the eclipse on 11 August.

BBC Radio 5live's Sarah Ransome: Clouds could make eclipse more exciting

"Realistically, climate statistics suggest that England is the least suitable land location from which to view the eclipse except for parts of India and Pakistan where monsoon cloudiness dominates," it says.

Nasa's calculations are based on weather data which includes southern England having only a third as many cloud free days in August as parts of central Europe.

Aim for Black Sea

The space agency's Website says the eclipse will start in the dismal cloudiness of the North Atlantic, with the weather steadily improving as it makes its way as far as the Middle East.

The best chances of clear skies can found along the shores of the Black Sea. Nasa says Iran offers the most favorable weather along the entire track, though it adds that cautious observers may prefer the skies of central Turkey.

Beyond Iran, Nasa says the Indian monsoon will rapidly diminish the chances of a good view, with very cloudy skies of the Bay of Bengal as the sun sets.

For those in Europe, Paris, Vienna and Munich and even Bucharest offer a far better chance of sunny skies than Cornwall. Cornwall's eclipse co-ordinator Gage Williams tried to play down the prospect of grey skies.

He said that if it was cloudy the eclipse could be even more spectacular, with people seeing a thin black line in the distance moving towards them "like an express train".

"For astronomers wanting to measure the corona it will not be good if it is cloudy but it can be even more spectacular."