The rainfall forecasts that appear on local weather pages are made up of two main indicators: probability of precipitation and likely amount of precipitation.

Probability of Precipitation
The probability of precipitation is the percentage chance of any precipitation, either rain or snow, falling in the 24 hours to 9am on the following day. That is, if it is considered almost certain that some rain will fall, even if it will be very light, the probability will be close to 100%. Note the time period that the forecast covers. If rain is expected between 2am and 5am on Tuesday (for example, the overnight passage of a cold front), this will be included in Monday's probability.

Rain amount
The rain amount figure is the amount of rain that is most likely if rain occurs.