Wednesday, October 07, 2009

Tomorrow's Weather: 40% Chance of Rain

When you are told that there's a 40% chance of rain tomorrow, what do you think? When you see the hourly forecasts and learn that for each hour in the morning there's a 40% chance of rain but in the afternoon there's only a 30% chance of rain in each hour, what do you think?

Find out how to interpret these numbers by reading Nick Anthis at The Scientific Activist: Bad Math at The Weather Channel.

[Photo Credit: South African National Parks]


  1. 10 people sit around the desk at the Weather Channel. One of them asks, "who thinks it's going to rain tomorrow?" 4 people raise their hands. Therefore, there will be a 40% chance of rain.

  2. Thanks for the link! I'd encourage people to check out the comments section of my post, as the discussion there has probably been more informative than the original post.

  3. Weather Channel is run by a denialist who spares no effort to assert that there is no evidence for anthropgenic climate change. It's all the way downhill from there.


  4. I think it works like as how monetary decisions is made in this southpark episode.

  5. I've always interpreted the percentage as the intensity. 20% chance? A light drizzle. 90% chance? Thunderstorms! Sure, it's probably completely wrong, but since I never go outside it's not really a problem for me.