Extreme Weather: How Hot is Tokyo in Summer?

Recently a question was posed on Quora: “How is the Tokyo summer heat?”. Here’s the bulk of my answer:

…   June is the rainy season: not as hot, but, well rainy (though not every day). July is, apparently, the most humid Weather and Climate: Average monthly Rainfall, Sunshine, Temperatures, Humidity, Wind Speed. August is the hottest.

It’s been a long time – 35 years? – since I visited Arizona in summer, specifically Sun City West where my grandparents retired. What I remember, however, is the dry heat you mention. even coming from my hometown of Toronto, a place not known for being particularly hot at any time of the year, I was surprised that the 100-degree-plus days didn’t FEEL hotter than they did (seems to me the hottest temp during one of my visits was 116).

By contrast, a hot day in Tokyo reaches 35 degrees Celsius, sometimes topping 38 (100 degrees Fahrenheit). However, there are two additional factors to take into consideration: humidity, and the heat-island effect.

Offhand, I can’t find any useful stats on just how humid Tokyo can be in the summer, but I can recall days where the temp was around 38 and the humidity above 90%. According to the Heat Index calculator at the National Weather Centre, that works out to 178 degrees Fahrenheit. Now, that ain’t the average, as I say, and I’m not sure any days reached that high in the summer of 2016, but it gets there – and in the summer of 2015 there was a record number of straight days of temps above 35 celsius in early August – in fact I posted about it Big Sushi, Little Fishes: a japan blog

The other consideration is the heat-island effect. I don’t know of any way to calculate how much concrete can raise the ambient temperature of a city, but I do know that walking ib Shinjuku, say, on a hot summer day, with car and air conditioner exhaust, amidst crowds of sweltering people, and a hot wind blowing up the urban canyonland can be an overwhelming experience. Fortunately, there are bars and cafes and shops and department stores and the like, most with over-active aircon, in which to take refuge!

So yes, of course comfortable weather is a relative phenomenon, and coming from southern Arizona the temps may even be a little low compared to what you’re used to. But temperature is only part of the equation; people who know say that in summer Tokyo is a tropical climate, on par with Singapore and other hotspots in southern Asia.

Of course, life does go on – even in heat-island Shinjuku – and there are mountains nearby to escape to if the heat does get oppressive. So the heat and humidity is no reason not to visit in summer: it’s just a matter of adjusting your inner thermostat, so to speak!

One thought on “Extreme Weather: How Hot is Tokyo in Summer?

  1. I agree with you that heat is not a reason to avoid Japan in summer. Most people who visit will be on holiday so no strict dress code for them and there is air conditioning in the trains, buses. Also there are lots of matsuri in summer and green tea ice cream too…

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