When you forecast a 30% chance of rain does that mean that 30% of the area will get rain or that the area will get rain for 30% of the day?

A forecast that calls for a 30% chance of rain or snow means that 30% of the forecast viewing area will see precipitation (for a given time period).

WHAM-TV Meteorologists don’t use probability of precipitation (POP) forecasts often, but the NWS uses this type of forecast frequently. The method increases or decreasing the possibility of precipitation over certain areas. Normally isolated rain or snow would affect less than 30% of the area. Scattered rain, snow, or thunder could affect 30-70% of the area. Rain (likely) means that over 70% of the area could see rain.