Key Facts
• On April 11, central Tokyo reached 25.3℃ by 11 a.m., marking the first summer day this year.
• From 2023 to 2025, summer days in central Tokyo occurred in March; April summer days are rare (first time in 4 years).
• Recent first summer days in central Tokyo:
| Year | Date |
|---|---|
| 2022 | April 10 |
| 2023 | March 24 |
| 2024 | March 31 |
| 2025 | March 23 |
• Despite the slight delay, bodies are not yet acclimated; heatstroke risk remains in mid-April.
• Outdoor activities like daytime cherry blossom viewing require consistent hydration.
• Heatstroke prevention tips:
1. Begin body conditioning with moderately intense daily 30-minute exercise in slightly warm environments.
2. As summer nears, avoid heat, hydrate before thirst, wear cool clothes, and use sun protection.
3. Use air conditioning on unexpectedly hot days; monitor indoor temperature and maintain ventilation.
• Early air conditioner maintenance and testing are recommended.
Summary
On April 11, 2026, central Tokyo experienced its first summer day of the year, with temperatures reaching 25.3℃ by late morning. This is notable as the first summer day has typically occurred in March over the past few years, making this April occurrence the first in four years. Since bodies are not yet adapted to heat, there remains a risk of heatstroke even in mid-April. Residents and visitors engaging in outdoor activities such as cherry blossom viewing should prioritize hydration. Experts advise starting heat acclimation exercises early, maintaining hydration before feeling thirsty, wearing appropriate clothing, and using sun protection like hats and umbrellas. On unexpectedly hot days, using air conditioning to regulate indoor temperatures is important, along with monitoring room conditions and ensuring proper ventilation. Early preparation, including air conditioner maintenance, can help prevent heat-related illnesses as warmer weather approaches.
