Walk through Jinghong, the capital of the Xishuangbanna region in the far southwest of China, in the middle of April and you are likely to get very wet.

The culmination of the three day-long water-splashing festival that marks the Dai New Year is a riot of people racing around the streets of Jinghong and the surrounding villages, soaking every person in sight with buckets of water, hoses, water-pistols and water-filled balloons.

Foreigners come in for special attention; it is not unusual for visitors to be drenched the moment they get off the bus in Jinghong, which lies close to the border with Laos and Myanmar in the deep south of Yunnan Province. But there is far more to the water-splashing festival than just the chance for a free shower, because Jinghong and Xishuangbanna is where China meets Southeast Asia.

Everything about the region, from the palm tree-lined streets of Jinghong and the jungle-covered hills outside the city, to the steamy climate and the spicy local cuisine, is more redolent of Southeast Asia than the China of The Great Wall and the Forbidden City. Above all, Xishuangbanna is home to an array of ethnic minorities with close links to their cousins across the nearby frontiers with Laos and Myanmar, as well as Thailand. Uniquely for China, the blend of peoples and cultures here means it is a region where ethnic identity is more important than the colour of a person’s passport, or which side of the border you live on.

The water-splashing festival is perhaps the prime example of the trans-cultural nature of Xishuangbanna. Celebrated from 13 to 15 April, the festival marks New Year for the Dai ethnic minority, who make up one-third of the population of the region. Closely related ethnically, culturally and linguistically to the Thais, as well as to the Tai Lue people of northern Laos and eastern Myanmar, the water-splashing festival is the Dai version of Songkran, the Thai New Year that takes place at the same time.

At one time, Xishuangbanna, which is a corruption of the Thai "Sipsawngpanna", which means "12 Rice-Growing Districts", was part of a Dai kingdom that stretched south as far as Chiang Mai in northern Thailand. The Dai had their own King until 1953, when he abdicated under pressure from the ruling Chinese Communist Party. But far more than many of China’s ethnic minorities, the Dai have managed to maintain their cultural identity and traditions.

That is despite an influx of Han Chinese, who make up the majority of China’s population, into Jinghong. The water-splashing festival is when the Dai assert their difference from the Han, who celebrate New Year in late January or early February. Nevertheless, the festival has become enormously popular with Han Chinese tourists, who flock into Jinghong to get soaked alongside the locals and foreigners.

For the first two days, however, the festival is comparatively restrained. People wear their best clothes, while older women in the nearby villages don traditional costume such as printed sarongs and black headdresses decorated with silver jewellery, and gather with their families before visiting Dai temples and monasteries. There, they wash the statues of Buddha with water, a practise known as "Bathing the Buddha".

Originally, the now-blessed water would then be collected and poured on family members as a symbolic way of washing away the past year’s dirt and sorrows and to ensure good luck in the coming year. But, like Songkran in Thailand, the third day of the festival has now become a free-for-all, where water is hurled from apartment blocks and out of shops and restaurants, or sprayed from passing cars, at anyone in range. The wetter you get, the luckier you will be.

Once the festival finishes life in Xishuangbanna returns to its normal sleepy state. No one rushes in the tropical heat and life in the hill villages hasn’t changed radically, despite the fact that the region is now on the tourist map. Treks into the countryside offer the chance to meet not just the Dai, but the Wa, Jinuo, Hani and the Bulang minorities, all of whom have their own languages and customs. Just remember to take a towel if you’re in the area in mid-April.

The article 'The Dai water-splashing festival' was published in partnership with Lonely Planet.