This Is Why You Need to Check the Weather Forecast When You’re in Japan

It's accurate almost 100% of the time!

Have you ever been caught in the rain without an umbrella because the sky was clear in the morning? You might be surprised to see Japanese people take foldable umbrellas from their bags, as if they have known beforehand that the rain will come. It is because they are used to checking the weather forecast in the morning or even the night before.

Here are some reasons why you should check the weather forecast before you go out.

  • Thanks to the accurate data gathering and analysis skills, when the weather reporter says “it will rain tomorrow,” it is almost sure to rain.  
  • Especially in spring and autumn, the temperature gap between daytime and after sunset is huge. For example, it is not so unusual to have 10 degree celsius differences. Although you do not feel cold right now, you might consider to bring a jacket if you are likely to go out until late at night.
  • Due to the global climate change, Japan is not an exception to face the abnormal weather. The information is helpful to get ready in case of evacuation from heavy rain, heavy snow, typhoon, flood, and so on.

These are some unique words mentioned in the weather forecast.

  • 一時 ichiji:

When the weather condition is mostly a but changes to b, lasting less than 6 hours in a day (the official definition: ¼ of the time).

Example: 曇り一時晴れ kumori ichiji hare

It is going to be cloudy most of the day but the sun will shine in few hours.

Tips: It is easy to get confused with the time 1 a.m. or 1 p.m. because of the same pronunciation “ichiji”.

  • 時々 tokidoki:

When the weather condition changes from a to b on and off (the official definition: the interval time is longer than 1 hour) and the total amount of the time b is less than 12 hours in a day (the official definition: ½ of the time).

Example: 曇り時々晴れ kumori tokidoki hare

It is cloudy first, then sunny, but back to cloudy, repeating several times within a day.

  • のち nochi:

When the weather condition changes clearly from a to b.

Example: 曇りのち晴れ
 kumori nochi hare

It is cloudy in the morning but changes to be sunny.

When you hear “曇りのち雨 kumori nochi ame”, you must be careful. You should think about bringing an umbrella (foldable umbrella, if you do not want to get bothered by holding it for the whole time) with you because it means it will rain later.

  • 次第に shidaini:

When the weather condition gradually changes from a to b.

Example: 風が次第に強くなる。kaze ga shidaini tsuyoku naru.

The wind will get stronger.

When they mention a precipitation rate, it judges the percentage of rain or snow precipitating 1 mm or more in 24 hours in a weekly report, and in 6 hours in a shorter term report. The rate is described by rounding, in every ten places, from 0 to 100%. When the rate says 30%, it means that among 100 times reports, it actually rains or snows 30 times. Do not confuse this with the amount of rain or snow.

Sometimes they describe how much it will rain by telling us “xx mm per hour.” It might help you to imagine how much it actually is, below.

  • 10-19 mm: rather strong rain. It becomes hard to hear what others say, because of the rain drops sound.
  • 20-29 mm: strong rain. You will get wet even you put up the umbrella.
  • 30-49 mm: down-pouring of rain. You will get wet even you put up the umbrella. The rain pours as if you flipped a bucket full of water.
  • 50-79 mm: the umbrella does not work anymore. The rain pours like an waterfall.
  • More than 80 mm: the umbrella does not work anymore. It is dangerous to drive because of the white and poor visibility with splashes.

Source: Japan Meteorological Agency

 (24 June 2019)

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