Why do most online weather forecasts only state the chance of rain as a percantage, without stating the expected rainfall in millimetres? If there’s a 90% chance of rain, it matters a lot whether it will be 0.5 or 5mm

Question

Why do most online weather forecasts only state the chance of rain as a percantage, without stating the expected rainfall in millimetres? If there’s a 90% chance of rain, it matters a lot whether it will be 0.5 or 5mm

In: 29

Answer 1

Weather forecasters have done a poor job of communicating what chance of rain means. 50% chance of rain means that if you take the geographic area in question and watch it for the period of time in question, half of the area will be rained on. Your driveway could be wet and neighbor’s could be dry… still 50%. It doesn’t mean “given these conditions, half of the time it WILL RAIN and half of time it WILL NOT RAIN. Meteorologist don’t have enough data, and it isn’t practical to narrow down specific locations, so they basically just say “Atlanta” has a 90% chance of rain instead of attempting to say “Main Street” will be rained on from 8:00am to 3:00pm.