A "30% chance of rain" in a weather forecast means there is a 30% probability that measurable precipitation (usually at least 0.01 inches) will occur at any given point in the forecast area during the specified time period (e.g., afternoon, evening)

. This percentage is calculated by meteorologists as the product of two factors:

• Their confidence that precipitation will occur at all during the time period
• The expected coverage area of the precipitation within the forecast region

For example, if the forecaster is 60% confident that rain will develop and expects it to cover 50% of the area, the chance of rain would be 30% (0.6 × 0.5 = 0.3)

. It does not mean:

• That it will rain for 30% of the time
• That 30% of the area will definitely get rain
• That you personally have exactly a 30% chance of getting wet

Instead, it means that under similar weather conditions, rain would occur about 30% of the time or that 30% of forecast model runs predict rain

. So, you might get rain, or you might stay dry, but there is a roughly one- in-three chance of measurable rain somewhere in the forecast area during the given period

. In summary, a 30% chance of rain is a probabilistic forecast indicating a moderate likelihood of rain occurring at any point in the area during the specified timeframe, based on forecaster confidence and expected coverage.