Bangkok in September: Is it Really The Rainiest Month? (Yes.)

I won’t lie to you or bury the lede. September is the rainiest month of the year, when the monsoon dial is turned to 11, so to speak (Spinal Tap, anyone?).

But if you don’t mind some intense and moody tropical vibes, and the joy of finding spots of sunshine and breaks in humidity between the occasional torrential downpour, September in Bangkok is not a terrible option. This is a city of over 11 million people after all. Surely a little rain (or even a lot of rain) can’t grind it to a halt.

The rain now arrives with swifter, heavier bursts, but with it, you’ll find the cheapest hotel deals all year and lower tourist arrival numbers than virtually any other month.

Average Weather in Bangkok in September

• Average highs/lows: Around 32 °C during the day and 25 °C at night source (for those who need Fahrenheit, think 90 °F during the day and down to a pleasant 77 °F at night)
• Record extremes: Historically, daytime highs have reached 36 °C, while lows have dipped to 23–24 °C on cooler nights source
• Average humidity: Sky-high at 78–85%—one of the most humid months of the year source
• Average rainfall: 320–335 mm across the month (≈13 inches) source
• Chance of rain on a given day: Expect rainfall on 20–23 days, meaning you’ve got roughly a 70–75% chance of encountering rain on any given day. Fun odds! source

The Truth About Rain in Bangkok in September

Normally, I try to make it seem like it won’t be as bad as it seems when it comes to the rainy season in Bangkok. But September is a different beast.

Asking my fellow Bangkok-dwelling friends, they agree — there’s no buts about it, Bangkok in September is as rainy as it gets here, especially when a tropical storm system rolls through the area.

Since it’s inevitable, simply be prepared, plan more indoor time, and take advantage of the breaks in the rain to go see the things that are outdoors-specific.

Tips for Bangkok in Monsoon Season

• Use the Windy app to (try to) track the storms. It’s not perfect but it’s the best app I’ve used for detailed weather data — above is an example of a predicted storm.
• Pack an umbrella or lightweight poncho. Better yet, bring both. If you get caught without one, 7/11 is both a shelter and a haven selling the essentials you need to re-emerge back into the storm, properly equipped this time.
• Schedule your days in pencil. While normally rain patterns can be a bit more predictable in other parts of the year — tending to rain more in the afternoon and evenings as opposed to the mornings — in September, rain follows very little rules. You can use an app like Windy to try to track the rain…. but it’s harder than it seems to predict anything.
• BTS, BTS, BTS. With a side of MRT. Taxis in the rain are absolutely gridlocked, and motorbike taxis can be very dangerous in the rain.

Traveling in Other Parts of Thailand in September

If you are planning a trip to Thailand in September no matter what, let me help you pick the best itinerary for what to include (and where to skip) during this month if you want the best weather.

1. Gulf Islands (best bet): Koh Samui, Koh Phangan, and Koh Tao are typically drier in September than the Andaman side of Southern Thailand. On these islands, the actual heavy monsoon season really hits somewhere between October and December. You’ll still get some rain (you can’t get off that easily!).

2. Central Thailand: Other places in Central Thailand (Ayutthaya, Pattaya, Hua Hin, Kanchanaburi, Khao Yai National Park, etc.) get quite a bit of rain in September but are less prone to flooding than other more vulnerable parts of Thailand, so they’re still options for visiting.

3. Northern Thailand: September up north can be unpredictable, and I don’t really recommend it. Large cities like Chiang Mai usually handle the rain reasonably well, but rural and mountainous areas are more vulnerable — even large cities like Chiang Rai can be hit really hard. In fact, last September brought some of the worst flooding Chiang Rai had seen in nearly a century.

Places I’d skip: Phuket, Krabi, Koh Lanta, Koh Phi Phi, Koh Lipe (basically anywhere on the Andaman Sea side of Thailand), also Chiang Rai and surrounding rural areas and Isan Region.