The accuracy of forecast generally decreases while the error generally increases with forecast period.There are 5 categories of probability as follows:įor every 100 forecasts with a 'high' probability, there are about 70 times or more with an average accumulated rainfall of 10 mm or above in actual observation.įor every 100 forecasts with a 'medium high' probability, there are about 55 to 69 times with an average accumulated rainfall of 10 mm or above in actual observation.įor every 100 forecasts with a 'medium' probability, there are about 45 to 54 times with an average accumulated rainfall of 10 mm or above in actual observation.įor every 100 forecasts with a 'medium low' probability, there are about 30 to 44 times with an average accumulated rainfall of 10 mm or above in actual observation.įor every 100 forecasts with a 'low' probability, there are about less than 30 times with an average accumulated rainfall of 10 mm or above in actual observation. around the mean daily rainfall in rainy season) or more on that day. The PSR forecast on each day indicates the probability of the accumulated rainfall generally over Hong Kong reaching 10 mm (i.e.

The Probability of Significant Rain (PSR) forecast provides users with additional reference on rainfall amount and forecast trend for the coming 9 days.For detailed description of today's weather forecast, please refer to ' Local Weather Forecast'. '9-day Weather Forecast' provides general indications of the trends in weather for the coming 9 days.This middle 50% range (between 25th and 75th percentiles) is calculated based on the maximum/minimum temperature and relative humidity data within a 5-day period centred on that day in the 30 years from 1991 to 2020.

Weather 10 days