The space agency's website puts the chances of a stationary observer in southern England seeing the eclipse in a clear sky on 11 August at no more than 45 per cent.
The chances of clear skies are higher in Paris, Vienna and Munich and significantly higher still in Romania, where the likelihood of good visibility is more than 60 per cent. In Isfahan, Iran, eclipse watchers will have more than a 90 per cent chance of a clear view.
The Nasa calculations are based on weather data that includes southern England having only a third as many cloud-free days in August as parts of central Europe. Parts of Iran and Turkey, where theeclipse will be visible, have more than four times as many cloud free days as England.
Outlining the weather prospects for the eclipse in the British Isles, Nasa suggests that England has been lucky with the summer timing and the path of the solar eclipse because Land's End and the Lizard are two of the sunniest places in the country.
"Realistically, however, 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.
Gage Williams, Cornwall's eclipse co-ordinator, is not deterred by the prospect of grey skies. He said the sharp last-minute change in temperature caused by the eclipse could effect the chances of cloud and he said that if it was cloudy the eclipse could be even more spectacular.
He explained that people watching the eclipse on a cloudy day would see a thin black line in the distance moving towards them "like an express train.
"One of the fascinations of eclipses is that the weather makes each one different," he said. "For astronomers wanting to measure the corona it will not be good if it is cloudy but it can be even more spectacular."Reuse content