Weather in Bangkok in September

How September compares

September is the 10th warmest month of the year in Bangkok and ranks 8th of 134 destinations we compare for September - see where else is hot in September. Within Thailand it is 1st of 6 (Thailand in September). Against London's average high of 18.6°C in September, Bangkok is 12.3°C warmer by day and 13.7°C warmer at night.

Daytime and night-time in September

The typical September day in Bangkok peaks at 30.9°C, but that is an average: the warmest 10% of days reach 32.5°C or more. About 100% of days top 25°C and almost every pass 30°C. Nights average 24.9°C; one night in ten drops to 24.1°C or lower, so pack a layer for evenings. Between 1991 and 2020 the hottest September day here reached 36.2°C (2001-09-17) and the coldest night 22.3°C (2000-09-18).

Rain in September

Wet (more than 8 rainy days): about 26 days with 1 mm or more, 241 mm in total. Year to year it varies a lot - the wettest September was 2012 with 530 mm, the driest 2001 with 139 mm. Humidity averages 82%, which makes the heat feel heavier than the thermometer suggests.

Sea temperature in September

The sea averages 29.4°C - warm enough to swim (22°c+). Depending on the year it ranges from 29.0°C to 29.9°C. For the warmest sea here, come in May (30.6°C).

Sunshine and daylight

Around 1.5 hours of sunshine a day (estimated from cloud cover), 12.1 hours of daylight: the sun rises about 06:07 and sets about 18:20 local time in mid-September. Average cloud cover is 88%.

Is September a good time to visit Bangkok?

It is a reasonable choice: hot days but expect showers. The best months for Bangkok on our scoring are December, January, November; months averaging 25°C or more: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec.

Hot days, humid air and little relief at night

September may sit towards the cooler end of Bangkok’s year, but it is not cool by UK standards. London’s September daytime high is 18.6°C, so the change on arrival is considerable. Humidity averages 82%, making breathable clothing and a pace you can sustain more useful than an ambitious outdoor schedule. Keep midday plans light and leave room for breaks somewhere cool. Night-time temperatures stay warm, so evenings are not a reliable chance to cool down outdoors. Pack loose, lightweight clothes rather than autumn layers, and prioritise comfortable accommodation with cooling if warm nights tend to disturb your sleep.

Rain is the main reason to reconsider

With rain on about 26 days, wet weather needs to be part of the plan rather than an occasional inconvenience. That does not mean every rainy day is a washout, but a tightly timed outdoor itinerary leaves little room to adapt. Carry compact rain protection, choose footwear that can cope with getting wet and keep indoor alternatives available. Sunshine averages only about 1.5 hours within 12.1 hours of daylight, so long days do not translate into long sunny spells. September is a reasonable choice if you are comfortable changing plans; it is a poor fit if reliable sunshine is central to the holiday.