If you can choose, come in spring. Yilan is wet: the weather station in the county seat averages 2,745 mm of rain a year, on about 190 days. And unlike the west coast, its wettest season is autumn and winter, when the northeast monsoon blows straight off the sea into the Lanyang Plain. Summer has fewer rain days, but it brings the typhoons.
Weather by month
These are the Central Weather Administration's averages for the Yilan weather station, 1991 to 2020. A rain day is any day with at least 0.1 mm.
| Month | High / low (°C) | Rain (mm) | Rain days |
|---|---|---|---|
| January | 19.7 / 14.0 | 155 | 17.5 |
| February | 20.4 / 14.4 | 147 | 15.5 |
| March | 22.7 / 16.0 | 115 | 16.8 |
| April | 25.7 / 18.8 | 126 | 15.0 |
| May | 28.5 / 21.7 | 223 | 17.9 |
| June | 31.4 / 24.3 | 190 | 14.5 |
| July | 33.2 / 25.6 | 140 | 8.9 |
| August | 32.8 / 25.4 | 243 | 11.7 |
| September | 30.6 / 24.0 | 410 | 15.2 |
| October | 27.1 / 21.3 | 428 | 18.5 |
| November | 24.2 / 18.7 | 336 | 19.5 |
| December | 20.9 / 15.5 | 232 | 18.5 |
How we read them: March and April are mild and the lightest months for total rain, though still often damp. July has the fewest rain days, but it's hot. September to December bring the most rain, and November has the most rain days of the year.
The winter rain
From autumn, the northeast monsoon (東北季風) brings moist air in off the sea, and Yilan, facing northeast, takes the rain. The northeast gets its heaviest rain of the year once autumn sets in, while central and southern Taiwan stay dry. Expect grey skies and drizzle for days at a time from October into the new year. It's not a reason to stay away, just a reason to plan for it: this is the season for hot springs and a rainy-day plan.
Typhoon season
July to September is Taiwan's typhoon season. Since 1911, August has seen the most typhoons strike Taiwan, followed by July and September, and October to December still account for about 14%. Even a near miss matters here. In October 2026, Typhoon Champi passed offshore, but the CWA still expected 400 to 600 mm of rain in Yilan's lowlands, and the county closed offices and schools for two days. When a typhoon comes, trains and buses can be cut, boats stay in port and mountain roads close. In these months, keep a spare day and watch the CWA forecast.
Guishan Island season
If Guishan Island is on your list, come between March 1 and November 30, when landings are open. The island closes for the winter. Even in season it closes on rough days: the wind and the waves decide.
Status: the Scenic Area suspended landings for November 1, 2026 because of the tides. The 2026 season ends November 30; check the Scenic Area's Guishan Island site on the day.
Festivals by season
- Spring (late March to May): the Yilan Green Expo (宜蘭綠色博覽會) at Wulaokeng in Su'ao. In 2026 it ran from March 28 to May 10.
- Dragon Boat Festival (May or June): the Erlong River dragon boat race (二龍競渡) in Jiaoxi. Two villages have raced here for more than 220 years, in boats with no dragon heads.
- July and August: the Yilan Children's Festival (宜蘭國際童玩藝術節) at the Dongshan River Water Park. In 2026 it ran from July 4 to August 16. Check next year's dates on the official festival site before you plan around it. → The Children's Festival · Yilan with kids
- End of the seventh lunar month (August or September): Qianggu (搶孤) in Toucheng, in the years it is held, where teams climb greased poles to a tower of offerings on the night the Ghost Month ends.
- November: silvergrass on the Caoling Historic Trail above Dali. The 2026 Caoling Silvergrass Festival was moved to November 14 to December 13 after typhoon damage to the trail. → The Northeast Coast
→ Festivals and seasons · What's on
Good to know: whatever the season, long weekends and Lunar New Year fill the trains and jam Freeway 5. Book train seats early, or come midweek. → Booking trains to Yilan
Sources: Central Weather Administration, monthly means for Yilan, seasonal climate, Yilan weather station and typhoon handbook (2026); Focus Taiwan on Typhoon Champi; Northeast and Yilan Coast National Scenic Area, Guishan Island rules and landing notices; Scenic Area news, silvergrass festival; Yilan County Government, Green Expo 2026; PTS on the Erlong dragon boat race; Liberty Times on the 2026 Yilan Children's Festival; Yilan Children's Festival official site (checked November 2, 2026); UDN on the Toucheng Qianggu. Checked November 2026.