Temperature records for Isesaki (Gunma)
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Temperatures over the 3 months before and after
The gray bands show the range that the high (upper band) and the low (lower band) fell within on each day over the 30 years 1996–2025 (between the 10th and 90th percentiles, so about 80% of the 30 years fall within it). The shading between the solid and dashed lines marks days when the high was above normal (warm colors) or below normal (cool colors).
Show the values by date
| Date | Observed high | Observed low | Normal high | Normal low | Range of highs | Range of lows |
|---|---|---|---|---|---|---|
| Aug 1 | 36.5°C | 25.4°C | 33.2°C | 23.7°C | ||
| Sep 1 | 27.6°C | 21.6°C | 30.5°C | 22.1°C | ||
| Oct 1 | 32.2°C | 18.9°C | 25.1°C | 16.7°C | ||
| ― | ||||||
| Dec 1 | 14.1°C | 4.0°C | 10.2–18.9°C | 0.8–7.3°C | ||
| Jan 1 | 10.0°C | -0.3°C | 6.3–13.4°C | -3.8–2.3°C | ||
| Jan 31 | 9.6°C | -0.6°C | 7.1–13.4°C | -3.9–2.5°C |
These are statistics compiled from observations for 1996–2025 (30 years), not a weather forecast for any particular day. For the latest forecasts, see the JMA website.
― on the normal curve
Monthly normals for Isesaki
Temperature (monthly normals)
The lines show monthly normals: the upper line is the monthly mean of the daily high and the lower line the monthly mean of the daily low, and the middle line is the monthly mean temperature. Touch the point for a month to read its values. Normals are the 1991–2020 average.
Precipitation (monthly normals, mm)
Table of monthly normals
| Month | Mean | High | Low | Precipitation |
|---|---|---|---|---|
| Jan | 4.1 | 9.4 | -0.6 | 28.8 |
| Feb | 4.9 | 10.4 | 0.0 | 25.3 |
| Mar | 8.4 | 14.0 | 3.1 | 49.8 |
| Apr | 13.7 | 19.6 | 8.2 | 73.5 |
| May | 19.1 | 24.9 | 13.9 | 99.3 |
| Jun | 22.6 | 27.6 | 18.5 | 139.9 |
| Jul | 26.3 | 31.2 | 22.4 | 190.4 |
| Aug | 27.4 | 32.5 | 23.5 | 169.9 |
| Sep | 23.5 | 28.2 | 19.8 | 184.4 |
| Oct | 17.6 | 22.3 | 13.6 | 149.7 |
| Nov | 11.6 | 16.8 | 6.8 | 43.0 |
| Dec | 6.3 | 11.8 | 1.5 | 27.1 |
Temperatures are in degrees Celsius (°C) and precipitation in mm. Blank cells have no normal.
Annual mean temperature (1996–2025)
The yearly average of the daily mean temperature (the line is broken in years with many missing values). This station's observing conditions changed on July 27, 1998; January 1, 2003; February 17, 2009; March 2, 2021 (for example, a relocation or new instruments), so the statistics may not be continuous across those dates.
The normals listed here are averages over the 30 years from 1991 to 2020. They are fixed values that stay the same until the next revision of the normals, and they show how warm or cold that month usually is in that area.
All-time records
Records are statistics as of November 1, 2026. The statistical period differs by element, depending on when observations began or the station moved.
| Record | Value | Date | Records began |
|---|---|---|---|
| Highest temperature | 41.8°C | Aug 5, 2025 | Jul 1998 |
| Lowest temperature | -6.8°C | Jan 10, 2021 | Jul 1998 |
| Highest daily minimum | 28.6°C | Aug 4, 2025 | Jul 1998 |
| Lowest daily maximum | 0.7°C | Feb 8, 2014 | Jul 1998 |
| Heaviest daily rainfall | 258.5 mm | Sep 1, 2011 | Jul 1998 |
Top 5 highest temperatures
| Rank | Value | Date |
|---|---|---|
| 1 | 41.8°C | Aug 5, 2025 |
| 2 | 40.5°C | Aug 11, 2020 |
| 3 | 40.3°C | Jul 1, 2022 |
| 4 | 40.2°C | Jun 25, 2022 |
| 5 | 40.1°C | Aug 2, 2025 |
12-month dry-day calendar
The dry-day rate is the share of years with no precipitation (rain or snow) of 1 mm or more on that day (daily precipitation under 1 mm, smoothed over 4 days either side). It is based on observations for 1996–2025 (30 years).
The deeper the amber, the more years that day stayed dry (the legend above shows the colors). Each row ends with the monthly average; detailed values are in the monthly table below.
Monthly averages through the year
How the monthly average dry-day rate changes over the 12 months (the axis fits the range of values). The values match the monthly table below.
Monthly table of dry-day rates and climate
| Month | Dry-day rate | 2 days in a row | 3 days in a row | Windy days | Sunshine (avg.) | High (avg.) | Low (avg.) | Comfort |
|---|---|---|---|---|---|---|---|---|
| Jan | 90.9% | 84.8% | 79.0% | 8.4% | 6.8 h | 9.4°C | -0.6°C | Fair |
| Feb | 86.3% | 75.5% | 65.7% | 12.2% | 7.0 h | 10.4°C | 0.1°C | Fair |
| Mar | 78.2% | 63.7% | 51.7% | 14.0% | 6.8 h | 14.3°C | 3.5°C | Comfortable |
| Apr | 73.7% | 57.8% | 45.2% | 7.3% | 6.6 h | 19.7°C | 8.6°C | Comfortable |
| May | 69.3% | 52.2% | 38.0% | 3.6% | 6.0 h | 24.6°C | 13.9°C | Comfortable |
| Jun | 60.9% | 40.5% | 26.9% | 1.0% | 4.3 h | 27.6°C | 18.6°C | Good |
| Jul | 56.7% | 38.0% | 27.2% | 0.2% | 4.5 h | 31.4°C | 22.7°C | Tough |
| Aug | 65.3% | 48.3% | 36.0% | 0.7% | 5.2 h | 32.5°C | 23.7°C | Tough |
| Sep | 61.5% | 45.0% | 33.0% | 1.1% | 4.5 h | 28.1°C | 20.0°C | Good |
| Oct | 72.8% | 57.7% | 45.5% | 2.5% | 5.0 h | 22.2°C | 13.6°C | Comfortable |
| Nov | 82.5% | 71.5% | 62.0% | 4.1% | 5.9 h | 16.9°C | 7.0°C | Comfortable |
| Dec | 88.6% | 80.8% | 73.9% | 5.8% | 6.5 h | 11.8°C | 1.6°C | Good |
"2 days in a row" and "3 days in a row" are the monthly averages of the share of years in which it stayed dry for 2 or 3 days from that day (counted from the actual consecutive records). "Windy days" is the share of days with a daily mean wind speed of 5 m/s or more. Sunshine averages include estimates from March 2021 onward at some stations. The month names link to monthly pages that compare stations across Japan.
Comfort over the 12 months
A guide that rates the comfort of each month on 5 levels from observations of dry-day rate, sunshine, wind, and temperature for 1996–2025 (30 years). The levels are also in the monthly table above.
This station's observing conditions changed on July 27, 1998; January 1, 2003; February 17, 2009; March 2, 2021 (for example, a relocation or new instruments), so the statistics may not be continuous across those dates.
These are statistics compiled from observations for 1996–2025 (30 years), not a weather forecast for any particular day. For the latest forecasts, see the JMA website.
About the Isesaki station
This station, at an elevation of 64 m, is on flat land where the southern foot of Mt. Akagi gives way to the Kanto Plain. The 41.8°C of August 5, 2025, is the highest temperature recorded at any station in Japan. In 2nd place are Hatoyama and Shizuoka, both at 41.4°C, a gap of 0.4°C.
That day, high temperatures lined up across Gunma Prefecture, with Kiryu observing 41.2°C and Maebashi 41.0°C. Isesaki also reached 40.5°C on August 11, 2020. The highest daily minimum on record is 28.6°C, shared by August 4, 2025, and July 29, 2024. Even in the normals, the maximum in early August is a high 33.6°C, and the daily rainfall record is 258.5 mm on September 1, 2011. Statistics run from July 1998, which places it among the newer stations in the prefecture.
Record values in this description are based on data collected as of September 2026.
Compare and explore
Nearby stations: Maebashi (about 12 km) / Kiryu (about 17 km) / Kami-Satomi (about 25 km)
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