The worst time to visit Thailand is generally during the peak rainy season, which runs from July to October. Here’s why:

1. Heavy Rain and Flooding

• The monsoon season brings intense rain, especially in September and October. Some areas experience daily downpours, which can last for hours. Flash floods are common, particularly in Bangkok and other low-lying regions, making it difficult to explore certain areas and causing transportation delays.

2. High Humidity and Unpredictable Weather

• Humidity levels are very high during these months, which can make sightseeing uncomfortable, especially for those not used to tropical climates. The weather can also be unpredictable, with sudden storms disrupting travel plans.

3. Limited Access to Some Islands and Beaches

• Popular islands in the Gulf of Thailand (like Koh Samui, Koh Phangan, and Koh Tao) and the Andaman Sea (like Phuket and Krabi) may have rough seas and limited ferry services. Water activities, such as diving, snorkeling, and boat tours, are often canceled due to unsafe conditions.

4. Fewer Outdoor and Adventure Opportunities

• Outdoor excursions, including trekking in the north (such as Chiang Mai and Chiang Rai) or exploring national parks, can be tricky due to muddy and slippery trails.

When to Consider Visiting Instead

• November to February is the best time to visit Thailand, with cooler and drier weather across most regions. This season offers the most enjoyable conditions for beach outings, island hopping, and exploring cities without the extreme heat or frequent downpours.

If you’re okay with fewer crowds and budget travel, you might still consider visiting during the early or late rainy season (May-June and late October), but keep a flexible schedule to adapt to the weather!