system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What does a 30% chance of rain actually mean?

Does that mean that 30% of the area will definitely get rain or that it's a 30% guess?
gpt
It's generally a combination of both of those.  You take the portion of the area you expect to experience measurable precipitation (at least 0.01 inches) and multiply it by the estimated chance that there will be rain in the forecast area.

For example, if your models show that there's a 50/50 chance of rain occurring, and the rain would be expected to occur over half the land in the region you're talking about, you'd multiply 0.5 by 0.5, giving you a result of 0.25.  Convert that to a percent and you have a 25% chance of rain.