Full-Month Osaka Climate Analysis: July Temperature and Humidity in 2024 vs. 2025
Recalculate the complete July observations and correct the old 79% humidity and “roughly doubled” claims.
2 min read
The old article reported Osaka's July 2025 mean humidity as 79% and said extreme-heat and hot-night counts roughly doubled. Recalculation of the complete July daily observations does not support those claims. Temperature and relative humidity are corrected separately.
Calculation
- Osaka station 47772
- July 1–31 in 2024 and 2025
- daily mean, maximum, minimum, and mean relative humidity
- days at or above 35°C use daily maximum
- days at or above 25°C use daily minimum
Results
| Complete July, Osaka | 2024 | 2025 | Difference |
|---|---|---|---|
| mean of daily means | 29.6°C | 30.2°C | +0.6°C |
| mean daily maximum | 33.5°C | 35.3°C | +1.8°C |
| days at or above 35°C | 13 | 17 | +4 |
| days with daily minimum at or above 25°C | 24 | 28 | +4 |
| mean daily relative humidity | 70.9% | 66.5% | -4.4 points |
| highest monthly maximum | 36.6°C | 38.7°C | +2.1°C |
The same method was applied to the 2024 and 2025 JMA daily tables.
Temperature measures were higher in 2025 while mean relative humidity was lower. The old explanation that higher humidity caused the difference is not supported by this table.
Corrections
- “79% mean humidity in 2025” → 66.5% mean of daily relative humidity
- “extreme-heat days roughly doubled” → 13 to 17 for the complete month
- “hot nights roughly doubled” → 24 to 28 under the daily-minimum proxy
- “worst WBGT in five years” → removed because WBGT was not calculated
- “cooling the brain improves concentration” → removed because the weather comparison did not test it
Relative humidity is not WBGT
Relative humidity changes with air temperature. The Japanese Ministry of the Environment's WBGT explanation describes a heat index incorporating humidity, radiant heat, and air temperature. Monthly mean relative humidity cannot reproduce a particular day's WBGT or personal health risk.
Limits
This is one Osaka station and one month. A daily minimum at or above 25°C is a simple daily condition, not a separately calculated nighttime interval. Use current local WBGT, alerts, indoor conditions, and personal symptoms for heat-health decisions.
Conclusion
Osaka's July 2025 mean daily temperature was 0.6°C higher, mean maximum was 1.8°C higher, and there were four more days at or above 35°C than in July 2024. Mean relative humidity was 4.4 points lower, so the old high-humidity explanation is corrected.
Primary sources checked
Important claims should also link to the relevant source in the article body.
- Osaka daily values for July 2024Japan Meteorological Agency · government · Checked: 2026-07-26
- Osaka daily values for July 2025Japan Meteorological Agency · government · Checked: 2026-07-26
- About the Wet Bulb Globe Temperature heat indexMinistry of the Environment, Japan · government · Checked: 2026-07-26