Yesterday as we drove around Bangkok, people standing by the sides of the roads threw buckets of water over the windscreen of our car. This throwing of water is is the most obvious celebration of Songkran (Thai New Year). Thais roam the streets with containers of water or water guns (sometimes nicely mixed with talc), or post themselves at the side of roads with a garden hose and drench each other and passers-by.
The throwing of water originated as a way to pay respect to people, by capturing the water after it had been poured over Buddhas for cleansing and then using this "blessed" water to give good fortune to elders and family by gently pouring it on the shoulder. Among young people the holiday evolved to include dousing strangers with water to relieve the heat, since April is the hottest month in Thailand (temperatures can rise to over 100°F or 40°C on some days). This has further evolved into water fights and splashing water over people riding in vehicles.
Nowadays, the emphasis is on fun and water-throwing rather than on the festival's spiritual and religious aspects, which sometimes prompts complaints from traditionalists. In recent years there have been calls to moderate the festival to lessen the many alcohol-related road accidents as well as injuries attributed to extreme behavior such as water being thrown in the faces of traveling motorcyclists.
It's a good job that this celebration doesn't exist in Sweden. To 'kasta vatten' - to throw water - can also mean to piss.
And you wouldn't want strangers in Stockholm to 'kasta vatten' on you as you cycle past minding your own business.