When Do Typhoons Usually Arrive? An Analysis of Typhoon Season Patterns
Seasonal distribution of typhoons in the Northwest Pacific and patterns of landfall in China.
When is the Typhoon Season?
The Northwest Pacific is the only ocean basin in the world where typhoons can form in all 12 months of the year, but their distribution is highly uneven. For China, July to September is generally considered the peak typhoon season (often referred to as the critical flood control period). Approximately 70% of all typhoons making landfall in China occur during these three months.
Monthly Breakdown
| Month | Characteristics |
|---|---|
| Jan–Apr | "Off-season" for typhoons; occasional open-ocean typhoons rarely affect China |
| May–Jun | Typhoon season begins; local South China Sea typhoons become active, with Southern China starting preparations |
| Jul | Peak landfall period begins; the subtropical high shifts northward, putting Southern and Eastern China on full alert |
| Aug | The month with the most typhoons (averaging nearly 6 formations); the northern limit of landfalls can reach Jiangsu, Zhejiang, Shanghai, or even further north |
| Sep | Autumn typhoons appear; sea surface temperatures remain high while cold air begins to move south, creating a risk of extreme disasters from combined wind and rain |
| Oct–Nov | Formation points shift southward, mainly affecting the coastal areas of Southern China and Hainan; late-season typhoons should not be underestimated |
| Dec | Closing period; occasional typhoons still form in the South China Sea, while open-ocean typhoons mostly recurve and dissipate |
Why is August the Peak Month for Typhoons?
Three conditions align perfectly in August: sea surface temperatures reach their annual peak (warm pool generally above 29°C), the position of the subtropical high is favorable (easterly winds on its southern flank guide typhoons westward), and the monsoon trough is most active (providing a continuous supply of typhoon embryos).
Why Are Autumn Typhoons More "Dangerous"?
After being heated throughout the summer, ocean heat content peaks in September and beyond, making it easier for autumn typhoons to rapidly intensify into super typhoons. Meanwhile, cold air becomes more active. When it interacts with a typhoon's circulation, rainfall intensity can multiply (historically, many catastrophic rainstorm events have been caused by the combination of "typhoon + cold air").
Regional Preparedness Calendar
- Southern China (Guangdong, Guangxi, Hainan): Prepare starting in June; the longest typhoon defense window (June–November)
- Taiwan Strait, Fujian, and Zhejiang: July to September is the absolute peak period
- Jiangsu, Zhejiang, and Shanghai: Be vigilant against northward-moving typhoons in August and September
- Shandong and Northeast China: Pay attention to the residual circulations of typhoons moving deep inland around August (e.g., the triple impact on Northeast China by Lekima in 2019, and Bavi, Maysak, and Haishen in 2020)