September · Vietnam
Best time to visit Cat Ba Island in September Weather, crowds & prices
Weather in Cat Ba Island in September
Average temperature 28°C, 399 mm of rain, about 15 days with 6+ hours of sunshine and 86% humidity — based on the five most recent complete years of ERA5 data (2021–2025).
September score
3.1/10
Ranked #12 of 12 months
- Avg temp
- 28°C
- Rainfall
- 399 mm
- Humidity
- 86%
- Days with 6h+ sun
- 15
- Crowd Density
- Quiet / Uncrowded
- Average Expenses
- $ · Budget Friendly ($)
September in Cat Ba Island scores 3.1/10 for nature and wildlife travel - ranked #12 of 12. Expect around 28°C, 399 mm of rain, and roughly 15 days with 6+ hours of sunshine this month.
Largest island in Halong/Lan Ha Bay featuring rainforest national parks, bioluminescent plankton, and kayaking.
September in Cat Ba Island — off-season conditions
September averages 28°C (82°F) and humidity near 86%, so the practical pattern is early mornings, a long midday break, and evenings back outside.
399 mm of rain puts this in monsoon territory — about 15 days with 6+ hours of sunshine across the whole month, and multi-day washouts are normal.
It scores 3.1/10 here, 12th of 12 months, against 7.9/10 in the destination's best month.
Pack the lightest breathable clothing you own, a hat, and more water than feels necessary, a proper rain shell rather than an umbrella, footwear you can get muddy.
Figure on low-season pricing, with crowds are light for this destination.
Flexible dates? November scores 4.8 points higher here — enough to change the trip.
Frequently asked
- What is the weather like in Cat Ba Island in September?
- In September, Cat Ba Island averages 28°C, 399 mm of rain, and about 15 days with 6+ hours of sunshine. Its climate-comfort score is 3.1/10.
- Is September a good time to visit Cat Ba Island?
- September earns a 3.1/10 climate-comfort score. Use the year-round chart to weigh the weather against your budget and crowd preferences.
- How much does it rain in Cat Ba Island in September?
- Expect about 399 mm of rain in September. Average humidity is 86% and there are about 15 days with 6+ hours of sunshine.
Curated in Cat Ba Island
Tickets & experiences
Things to do in Cat Ba Island
Cat Ba Island, Vietnam. Live activities and tours from GetYourGuide, matched to this destination.