What is Uchimizu? – Summer in Japan –

August 30, 2014 Juju Kurihara 6 Comments

August is nearly to the end but it´s still quite hot and humid in Japan. After two months of heat, people can be really tired. When I was small, my appetite was very small and only I wanted to eat was cold drinks or watery food such as somen noodles, watermelon or cucumber. I was in a swimming team back then and since the summer was the peak season, I would go training almost everyday. I´m not talking about having some splash. We had to swim three to five km a day. I don´t know how I was managing it with such a little food. 


Anyway, my swimmer life is another story. What I wanted to talk about is the summer heat. To begin with, Japan is situated in the subtropics area and it´s very hot and humid. Old Japanese people did thing about how to deal with this heat without using the technology we have now. Eating unagi was one of them. 

uchimizu 1

Another method is Uchimizu (打ち水). The word uchi comes from the verb, utsu means hit or strike. And mizu is water in Japanese. Do you hit the water? No, no. I guess it comes from the water hits the ground. 

What is it? If you have been in Japan during the summer, you may have seen the wet street and wondered, when did it rain? It wasn´t rain but people splash come water on the heated asphalt because ancient Japanese people believed uchimizu will cool the air down. 

This is not a belief but scientifically true. This is vaporization. Have you ever been told by your mother to dry your hair and body well after having a bath as a child? And she would tell you, "Dry yourself otherwise you´ll get cold", didn´t she? This is because the water remains on your warm body vaporizes and takes the warmth away from you. Then your body temperature will low and as a result, you get cold. It´s the same as sweating. You sweat to cool your body down. I know you don´t do it consciously but your body does. 

uchimizuAfter sprinkling the water on the hot concrete street, the heat evaporate and escape into the air. Since the asphalt doesn´t contain water like the earth, it needs to be watered. 

I don´t know if uchimizu can low the temperature 10 degrease but a few degrease, for sure and this little difference in summer is big. Also as you feel cooler, you may use less air conditioner. At the end, it´s eco-friendly. 

Talking about eco, it´s recommendable that you use used water, means the water left in the bath or the kids´ pool or the rainwater. Usually uchimizu is done during the morning or after dropping the temperature a little. The reason is if you sprinkle the water at the hottest time of the day, the water vaporises so quick that you are likely to feel even hotter and more humid. The last point for uchimizu is water bigger area. You don´t have to water whole street. You don´t even have to water your neighbours´ part of the street. Just in front of your house but widely. If you live in a flat and have a balcony, if works too. The breeze comes through the wet balcony will be a little cooler and the plants will be happier too. So why don´t you try it now?


Now, it seems like uchimizu has become an event in Japan. This year in Akihabara, more than 200 people joined. As long as we keep this tradition, we might be able to save energy and be nicer to the earth.




More Japanese custom

Kids´ footprints

The myth of plastic bottles

3rd of February

21st of March

4th of April

5th of May

8th of August

22nd November

22th of December


  1. Lorenzo Perugini 8 years Reply

    That’s one of the reasons why I so love Japan. They have a name for everything. It’s another indication of the exceptional care the japanese people put in everything they do, even the humblest action.
    Actually, this is a practice that has been done in my country (Italy) as well since ages – especially in southern Italy, where summer gets so hot. But I don’t think we’ve never thought of giving a specific name to that action!
    I think that giving a proper name to something is a way of showing respect for it, since once it has a name, you can easily remember it and tell it from any other thing.
    “Oh, I have to sprinkle water on the entrance of my house!” and “Oh! I have to perform Uchimizu” sound so radically different to me!

    • juju.kurihara 8 years

      Thanks for your comment, Lorenzo. It´s nice to know that you have the same custom in Italy. I lived in Spain some years and the summer was very hot. I don´t remember if people were doing uchimizu though. Some shops did “throw away” the dirty water after cleaning the shop… 

      I agree putting a name to the action makes the event more important in a daily life. Even though it´s the same concept that you throw away the used water but by calling it uchimizu and knowing the effect of it, it sounds much more ellegant than just “throwing dirty water away”.

  2. Pramod Kaushik 8 years Reply

    It is a very useful information to understand about various Japanese customs…..

  3. Mike Kato 8 years Reply

    Uchimizu works wonderfully, of course. I have used this method for years, starting from where I grew up in Southern California and now, living in Japan. It works on the street in front of the home, but also on very hot walls. The evaporating water draws heat away from the hot wall, cooling it down. This makes the inside of the walls – in the house – cooler. It probably only changes the temperature by less than one degree, but in the evening, the effect is even greater. This is because once cooled, the walls do not heat up again as easily as during the day. Not all uchimizu are the same! Timing is key!

    • juju.kurihara 8 years

      Thank you for your comment, Mike san.

      I didn´t think about the wall but I guess the function is the same. Exactly once the asphalt (or the wall) is wet, it´s slower to heat it again. It seems like people think more when there is not so many technologies.

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