Best time to visit Japan

Best months: May, June and April
Year: 2001-2020
Spread between cities: 85 (in January)

The answer for Japan is computed across 4 measured cities, and there May, June and April come out best on the twenty year normals for 2001-2020. That is an average of real places rather than a figure for the country as a whole, because no such figure exists.

75 percent of the 4 measured cities rank May among their own best four. The rest do not, which is the first sign that this is not one climate.

The widest disagreement is in January, where the measured cities sit 85 points apart: Naha scores best and Sapporo worst in the same month. A single best time for Japan hides that gap, and for part of the country it would be the wrong answer.

The numbers behind that: May averages 17.5 degrees across the measured cities, from Sapporo at 10 to Naha at 24.5, and brings about 148 mm of rain.

The months to avoid are January and February, and what decides it is the cold.

Each month is scored on its mean temperature, its rainfall and its humidity, taken from the provider twenty year normals for 2001-2020. The cities are Tokyo, Osaka, Naha and Sapporo. The comfort bands and the penalties are fixed and published, so a reader who disagrees with the ranking can see exactly which part of it they disagree with.

The source publishes a monthly mean and, separately, the highest and lowest values it recorded in twenty years. Those extremes are not a typical afternoon or a typical night, so nothing here is quoted as one. This page does not say what the daytime high usually is, because this source cannot say it.

Normals are not a forecast. They describe what twenty years averaged to, and any single year can sit well outside them. They also describe a model grid cell of roughly fifty kilometres rather than a weather station, so a coastal city and the sea beside it share one figure.