Nong Khai has a tropical climate with three seasons: hot (March to May), rainy (June to October) and cool (November to February). The cool season is the most comfortable for visiting, with pleasant temperatures and low humidity. The Mekong is at its highest and most dramatic during the rainy season.
Several festivals are worth timing a trip around. The Songkran Fair in April centres on Wat Pho Chai, where the revered Luangpho Phra Sai Buddha image is paraded through town. In May, the Bun Bang Fai (Rocket Festival) sees homemade rockets fired skyward to summon the rains -- raucous and unforgettable.
The most extraordinary event is Bang Fai Phaya Nak at the end of Buddhist Lent (usually October), when mysterious reddish fireballs rise from the Mekong at night. Locals attribute them to the Naga serpent of the deep. Thousands gather along the riverbank to watch, and the atmosphere is electric. The Thai-Lao Friendship Boat Race takes place around the same time, with long-boat crews racing on the Mekong.