Saturday wet. Sunday wet and windy. Monday blue skies and endless hours of sunshine.

Scientists have finally found proof for what weekday workers have always suspected - weekends get the worst weather and the sun comes out once everyone is safely back in the office.Climatologists Randall Cerveny and Robert Balling of Arizona State University said Wednesday that research into weather patterns on the east coast of North America showed the massive drift of pollution from the area naturally created clouds and rain.

"The most obvious culprit is the `natural' cloud-seeding effect created by the massive drift of East Coast pollution," they said in the scientific journal Nature.

As traffic builds, and factories crank up between Monday and Friday, pollution grows, spawning clouds for a wet weekend.

The two scientists examined daily emissions of carbon monoxide and ozone, cross-referencing the figures with rainfall, and they found the buildup of pollution and rainfall followed a seven-day cycle.

"Human effect on weather is the only explanation," said Balling.