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Monthly Forecast

Monthly Forecast for September 2025


Hong Kong is expecting:
1.
 normal to above-normal temperature
2.
 normal to above-normal rainfall



Additional information:
  1. The subtropical ridge is expected to extend westward over the southeastern part of China for most of the time in September 2025. Meanwhile, a broad trough of low pressure will be lingering over the central and northern parts of the South China Sea, favourable for the development of tropical cyclones over the South China Sea and seas near the Philippines.

Assessment (as of 29 August 2025):
  1. In the past month or so, sea surface temperatures of the central and eastern equatorial Pacific were near normal on the whole. Based on the latest oceanic observations as well as forecasts by a number of climate models around the world, the sea surface temperatures of the central and eastern equatorial Pacific are expected to be normal to below normal for autumn and winter this year.

  2. Taking into consideration of the impacts of global warming and latest ENSO status, different climate model forecasts and other objective forecast guidance, the temperature of September 2025 in Hong Kong is expected to be normal to above-normal, and the chance of normal to above-normal rainfall in the month will be slightly higher.


Note:
  1. The Observatory gratefully acknowledges the European Centre for Medium-Range Weather Forecasts, the Tokyo Climate Center of the Japan Meteorological Agency and the National Centers for Environmental Prediction of National Oceanic and Atmospheric Administration, USA for providing dynamical prediction model forecast and hindcast data to support the formulation of monthly forecast for Hong Kong.

  2. Monthly Forecast for October 2025 will be available around 1st October 2025.

  3. Monthly mean temperature and rainfall categorical forecasts charts.

  4. Ten days constitute a "ten-day period," and three such periods make up a month. The first ten days of each month are called “the first part of the month”, the second ten days are “the middle part of the month”, and the remaining days are referred to as “the latter part of the month”.

 
Monthly forecast charts provided by major climate centres:
Related links:
| Seasonal forecast | Annual outlook | El Niño and La Niña | Climate change |
For further information on this webpage, please contact Mr. W P Tse (tel:2926 8012, email:wptse@hko.gov.hk)