Climate Trends in Japan

• In Japan, the mean number of days with a daily maximum at or above 30 C (86 F) per year at 29 stations rose from 46.9 to 56.8 between the 1960s and the 2010s; the 2020s so far (4 years) average 65.3.
• In Japan, the mean number of days with a daily maximum at or above 35 C (95 F) per year at 29 stations rose from 2.9 to 9.4 between the 1960s and the 2010s; the 2020s so far (4 years) average 10.4.
• In Japan, the mean number of days with a daily maximum at or above 40 C (104 F) per year at 29 stations was 0.0 in both between the 1960s and the 2010s; the 2020s so far (4 years) average 0.0.
• In Japan, the mean number of ice days, with a daily maximum at or below 0 C (32 F) per year at 29 stations fell from 5.8 to 4.5 between the 1960s and the 2010s; the 2020s so far (4 years) average 3.7.

Each measure counts days in complete years only. A station is in a measure's set when it has complete years in every decade from the 1960s, so each chart compares the same places over time. A grey bar is a decade that is not over.

• In Japan, annual rain at 122 stations is shown as a percent difference from each station's own 1961-1990 mean, for 59 years from 1951 to 2024.
• The trend in annual rain is -0.2 percent per decade (95 percent interval -1.3 to +1.0), fitted to 59 years from 1951 to 2024. The interval includes zero, so the series does not separate a trend from year to year variation.

Annual rain against the 1961-1990 mean

The annual rain series uses stations with at least 50 complete years since 1951 and a 1961-1990 baseline. The decade charts use fixed sets of stations, the same in every decade from the 1960s. A dry day has less than 1 mm (0.04 in) of rain.

• In Japan, the longest run of hot days in a row in the data is 21 days, at Yokosuka (Japan), from 30 July 1994 to 19 August 1994.
• In Japan, the longest run of days in a row at or above 40 C in the data is 3 days, at Yokosuka (Japan), from 3 August 1994 to 5 August 1994.
• In Japan, the longest run of frost days in a row in the data is 151 days, at Asahikawa (Japan), from 13 November 1987 to 11 April 1988.
• In Japan, the longest run of ice days in a row in the data is 93 days, at Omu (Japan), from 23 December 1983 to 24 March 1984.
• In Japan, the longest run of dry days in a row in the data is 59 days, at Saga (Japan), in 1967.
• In Japan, the longest run of wet days in a row in the data is 43 days, at Wajima (Japan), in 1984.
• In Japan, the longest run of longest run of nights at or above 25 c in the data is 96 days, at Futenma (Japan), from 8 June 1980 to 11 September 1980.

Longest run of days at or above 35 C

Consecutive days with a daily maximum at or above 35 C (95 F).

Longest run of days at or above 40 C

Consecutive days with a daily maximum at or above 40 C (104 F).

Longest run of frost days (minimum at or below 0 C)

Consecutive days with a daily minimum at or below 0 C (32 F).

Longest run of ice days (maximum at or below 0 C)

Consecutive days with a daily maximum at or below 0 C (32 F).

Longest dry spell (days under 1 mm of rain), within one year

Consecutive days with less than 1 mm (0.04 in) of rain, the longest run within a year. The dates are not kept, so the list gives the year (within the year).

Longest wet spell (days with 1 mm or more of rain), within one year

Consecutive days with 1 mm (0.04 in) or more of rain, the longest run within a year. The dates are not kept, so the list gives the year (within the year).

Longest run of nights at or above 25 C

A run belongs to the year it started in, even when it ran on into the next year. A station appears once per list, with its longest run in a complete year. Dry and wet spells are the longest run within a year. Lists use complete years only, so a long run in a year with gaps in the record is not counted.

• In Japan, the largest reported one day rise in the daily maximum is 22.2 C (40.0 F), at Hiroo (Japan) on 3 May 1969.
• In Japan, the largest reported one day drop in the daily maximum is 24.5 C (44.1 F), at Abashiri (Japan) on 25 April 1998.
• In Japan, the largest reported one day rise in the daily minimum is 20.7 C (37.3 F), at Kutchan (Japan) on 12 February 1956.
• In Japan, the largest reported one day drop in the daily minimum is 18.6 C (33.5 F), at Obihiro (Japan) on 5 January 1963.
• In Japan, the largest reported range between the high and the low of one day is 28.3 C (50.9 F), at Matsumoto (Japan) on 21 March 1971.
• In Japan, the smallest reported range between the high and the low of one day is 0.0 C (0.0 F), at Ibukiyama Mtn (Aut) (Japan) on 25 May 1956.

Caveat.Single readings can still be instrument errors that quality control missed. A station with one faulty value can top a list, so read each entry as a reported value, not as a confirmed event.

Biggest one day rise in the daily maximum

The largest increase in the daily maximum temperature from one day to the next. Values are in degrees Celsius with Fahrenheit beside them.

Biggest one day drop in the daily maximum

The largest decrease in the daily maximum temperature from one day to the next. Values are in degrees Celsius with Fahrenheit beside them.

Biggest one day rise in the daily minimum

The largest increase in the daily minimum temperature from one day to the next. Values are in degrees Celsius with Fahrenheit beside them.

Biggest one day drop in the daily minimum

The largest decrease in the daily minimum temperature from one day to the next. Values are in degrees Celsius with Fahrenheit beside them.

Widest range between the high and the low of one day

The largest difference between the highest and the lowest temperature of the same day. Values are in degrees Celsius with Fahrenheit beside them.

Narrowest range between the high and the low of one day

The smallest difference between the highest and the lowest temperature of the same day. Values are in degrees Celsius with Fahrenheit beside them.

Only stations with at least 10 complete years are listed, and a station appears once per list.

• In Japan, the share of stations with a hot and dry summer is shown for each year from 1951 to 2022, for 152 stations with at least 20 complete summers in 1961-1990. Each year counts the stations of that set with a complete summer in the year.
• In Japan, 9.1% of station summers in 1961-1990 were hot and dry (4,348 station summers).
• In Japan, 16.4% of station summers in 2008-2022 were hot and dry (1,551 station summers).
• In Japan, 1994 had the highest share: 63.6% of 11 stations (7).

A summer is hot when its mean daily maximum is at or above the station's 80th percentile of its 1961-1990 summers, and dry when its rain is at or below the 20th percentile. A summer is hot and dry when it is both. Summer is June to August north of the equator and December to February south of it, labelled by the year of its first month.

Share of stations with a hot and dry summer

The ten most extreme station summers

Ranked by the temperature z score minus the rain z score against the station's own 1961-1990 mean and standard deviation (at least 0.3 C and 5 mm). A summer is labelled by the year of its first month.