Answer: Saturday

Bluesman T-Bone Walker might have sung “They call it stormy Monday, but Tuesday’s just as bad…” but if he wanted to sing about the stormiest day of the week, he should have been singing about Saturday.

Saturday isn’t just the day of the week most likely to have rainfall, but it’s an example of human-driven weather patterns. The Monday-to-Friday work week generates a steadily rising amount of pollution over the course of the week from all manner of sources: workers commuting, dust from industrial processes, etc.

All those tiny bits of pollution rise in the atmosphere and serve as nucleation points for rain drops. By Saturday, a week’s worth of heavy weekday traffic has drifted up and done an admirable job seeding rain clouds–so the next time it rains down on you and ruins your Saturday barbecue, curse Mother Nature for bringing the work week to your weekend.