Can I trust a 15-day weather forecast?

A 15-day forecast can be useful for identifying broad trends, but it should not be treated as a precise prediction of exact rainfall or temperature on a particular hour. Forecast uncertainty increases with time. Use longer-range forecasts to understand whether a period is likely to be generally warmer, cooler, wetter or drier than normal. For important decisions, recheck the forecast as the date approaches and rely more heavily on short-range forecasts.