Laos Vientiane Weather in September — Climate Guide
September in Vientiane is moderate
September is moderate for Vientiane.
WARNING: September is Vientiane's wettest month — 320mm + 19 rainy days + Mekong at peak flow. The city itself receives heavy daily rain. Power cuts at their most frequent (sometimes 2-3 times weekly).
The positive: year's lowest hotel pricing — boutique $30-70/night, Crowne Plaza + Settha Palace luxury $130-280, Pullman $130-260 (50-60% off peak). Tourist crowds essentially nonexistent.
Travel score
WARNING: Year's wettest month + Boat Racing Festival
September Weather at a Glance
September averages 88°F / 31°C highs and 73°F / 23°C lows with 19 rainy days and 320mm of rain — wettest month of the year. Humidity 83%. UV 9. Sunshine 5 hours. Mekong at year's peak flow.
September Travel Advice
Travel insurance with cancellation coverage absolutely essential. Plan luxury on-property itinerary + skip outdoor activities. Boat Racing Festival (Boun Suang Heua, varies September) — varies year-by-year, confirm dates 2-3 months ahead. The Mekong in front of the Vientiane waterfront is the race venue. Korean Chuseok (varies, mid-September) brief regional uptick.
Flying In from Overseas
Year's lowest international flight pricing. Direct connection via Bangkok $200-400 (year's lowest). Korean Chuseok holiday brings brief regional uptick. Western shoulder before October recovery.
September Pricing Trends
Year's lowest pricing: boutique $30-70/night, Crowne Plaza $130-280, Settha Palace $110-240. Flights $200-400 via Bangkok / Hanoi.
Vientiane September Weather Stats
Avg High
31°C
Avg Low
23°C
Rainy Days
19
320mm total
Sunshine
5h
Daily avg
Humidity
83%
very humid
UV Index
9
Very high
Wind
8 km/h
Gusts 22
Sea Temp
28°C
swimming Mekong rough
Crowds
Quiet
At attractions
September Sunrise & Sunset
Air Quality
PM2.5
18 μg/m³
PM10
32 μg/m³
Status
good
Feels-Like Temperature & Wind
Feels like
Daytime
35°C
Nighttime
24°C
Humidity and wind affect how the actual temperature feels.
Wind
8 km/h
Max gust 22 km/h
Activities Recommended for September
September Travel Pros & Cons
Pros
- Year's lowest pricing — 50-60% off peak
- Boat Racing Festival (Lao biggest annual)
- Tourist crowds at year-low
Cons
- WARNING: Year's wettest month
- Power cuts 2-3 times weekly
- Outdoor activities mostly impossible
September Events & Festivals
- WARNING: Year's wettest month (320mm)
- Boat Racing Festival (Boun Suang Heua, varies September) — Lao biggest annual celebration
- Korean Chuseok holiday imminent
- Year's lowest pricing — 50-60% off peak
Vientiane in September — Full Picture
WARNING: September is Vientiane's wettest month — 320mm + 19 rainy days + Mekong at peak flow. The city itself receives heavy daily rain. Power cuts at their most frequent (sometimes 2-3 times weekly).
The positive: year's lowest hotel pricing — boutique $30-70/night, Crowne Plaza + Settha Palace luxury $130-280, Pullman $130-260 (50-60% off peak). Tourist crowds essentially nonexistent.
September signature: Boat Racing Festival (Boun Suang Heua) — varies year-by-year on a September date — Lao's biggest annual celebration with village-vs-village long-tail boat races on the Mekong directly in front of the Vientiane waterfront. The Mekong at high flow makes the race spectacular. Largely unknown to Western travelers, this is a hidden gem for Asian cultural travelers who can time their visit.
Honestly, September is the hardest sell — only on-property honeymoon couples at luxury hotels (Crowne Plaza, Settha Palace, Pullman) consistently report good experiences. Outdoor-focused travelers should skip. Wait for November-February or May-June.
What to Wear & What to Pack
WARNING: Year's wettest month — rainfall 320mm. Fully waterproof gear + quick-dry layers + multiple clothing changes. Days 31°C / 88°F + nights 23°C / 73°F.
Packing Checklist
Seasonal Weather Overview
Spring (Mar·Apr·May)
33.7°C
23.3°C
7.3/mo
Summer (Jun·Jul·Aug)
31.3°C
24°C
18/mo
Autumn (Sep·Oct·Nov)
Current30°C
21.3°C
11/mo
Winter (Dec·Jan·Feb)
29°C
17.7°C
1/mo
Vientiane Monthly Weather Comparison
| Month | High | Low | Rain | Sun | Humid | UV | Crowd | Price |
|---|---|---|---|---|---|---|---|---|
| January (Best) | 28° | 17° | 1d·7mm | 8.5h | 70% | 8 | Busy | Peak |
| February (Best) | 31° | 19° | 1d·15mm | 9h | 65% | 9 | Busy | Peak |
| 33° | 22° | 2d·30mm | 8.5h | 60% | 11 | Moderate | Shoulder | |
| 35° | 24° | 6d·90mm | 8h | 65% | 11 | Busy | Peak | |
| 33° | 24° | 14d·200mm | 6.5h | 75% | 10 | Moderate | Low season | |
| 32° | 24° | 16d·240mm | 6h | 80% | 10 | Quiet | Low season | |
| 31° | 24° | 19d·280mm | 5.5h | 82% | 10 | Moderate | Shoulder | |
| 31° | 24° | 19d·300mm | 5h | 83% | 9 | Moderate | Shoulder | |
| 31° | 23° | 19d·320mm | 5h | 83% | 9 | Quiet | Low season | |
| 30° | 22° | 11d·150mm | 7h | 78% | 9 | Moderate | Low season | |
| November (Best) | 29° | 19° | 3d·25mm | 8.5h | 70% | 8 | Very busy | Peak |
| December (Best) | 28° | 17° | 1d·7mm | 8.5h | 70% | 8 | Busy | Peak |
View Other Months
Vientiane September Hotel Picks
Frequently Asked Questions
Is September a good time to visit Vientiane?
Vientiane in September is moderate. Tourist crowds are quiet and flight/hotel prices are low season.
What's the average temperature in Vientiane in September?
Vientiane September averages a high of 31°C and a low of 23°C.
Does it rain much in Vientiane in September?
Vientiane September averages 320mm of rainfall over about 19 rainy days.
What should I wear in Vientiane in September?
WARNING: Year's wettest month — rainfall 320mm. Fully waterproof gear + quick-dry layers + multiple clothing changes. Days 31°C / 88°F + nights 23°C / 73°F.
What time are sunrise and sunset in Vientiane in September?
Vientiane September sunrise is 05:55 and sunset is 18:00, with 12h 05min of daylight.
What's the air quality like in Vientiane in September?
Vientiane September air quality (AQI) averages 40, rated Good. PM2.5 averages 18μg/m³.
What activities are recommended in Vientiane in September?
In September, Vientiane is great for Hotel pool + spa stays, Boat Racing Festival (varies September), Lao cooking class.
Is September peak season in Vientiane?
Vientiane September crowds are quiet and prices are low season. You can travel relatively comfortably without long queues.
Best Months to Visit Vientiane
View Other Months
Why you can trust weather guide
Based in Chiang Mai for 8+ years, with 30+ countries visited across Southeast Asia, Japan, and Europe. Every detail in this guide is primary-source verified as of April 2026, with prices auto-refreshed via live exchange rate APIs. This isn't AI-generated boilerplate — it's written from the perspective of someone who has actually been there.