For many people, summer conjures up vivid images: blue skies, sweltering heat, fireworks, shaved ice (kakigōri), and the symphony of cicadas. In Japan, however, the question of when summer truly begins isn’t answered by a single date — it depends on whether you ask the calendar, the weather service, or local tradition.
Let’s explore how Japan defines the start of summer through its unique cultural lens, meteorological standards, and natural signs.
1. “Rikka” — The Traditional Calendar’s First Day of Summer
In traditional Japanese culture, the changing seasons are marked by the 24 sekki (二十四節気) — solar terms derived from the ancient Chinese lunisolar calendar.
- The first sekki of summer is called Rikka (立夏), meaning “start of summer.”
- Rikka generally falls around May 5th each year.
- According to this traditional system, Japan officially enters summer from Rikka onward.
However, these calendar dates often don’t match how the weather feels. Even after Rikka, early May often still brings mild spring temperatures, cool evenings, and occasional chilly days.
The Cultural Role of Rikka
While Rikka may seem disconnected from modern weather patterns, it still holds significance in:
- Seasonal greetings in letters and business communication
- Traditional tea ceremony seasonal themes
- Haiku poetry, where seasonal words (kigo) are carefully chosen based on the 24 sekki
2. The Meteorological Definition of Summer
The Japan Meteorological Agency (JMA) takes a more practical, temperature-based approach:
- A “summer day” (夏日) is defined as any day when the temperature reaches 25°C (77°F) or higher.
- In most areas like Tokyo, consistent summer days begin to appear in early to mid-June.
- By July and August, nearly every day qualifies as a full-fledged summer day.
Thus, for most Japanese people, summer feels like it starts in June, when temperatures rise, humidity increases, and the famous rainy season (tsuyu) arrives.
Tokyo Example:
- May: Transition from spring to early summer warmth.
- Early June: First consistent “summer days” with temperatures over 25°C.
- Late June to early July: Rainy season peaks.
- Mid-July to August: Full-scale summer heat sets in, often surpassing 30°C (86°F).
3. Nature’s Signals: Japan’s Deep Sensitivity to Seasonal Transitions
In Japan, the arrival of summer isn’t determined only by numbers — nature itself signals the seasonal shift through familiar sights and sounds.
Fireflies (Hotaru)
- From late May to June, fireflies light up rivers and countryside forests.
- The brief, magical season of firefly-watching is cherished as an early summer tradition.
Hydrangeas (Ajisai)
- June brings the peak bloom of hydrangeas, coloring parks and temple gardens in shades of:
- Purple
- Blue
- Pink
- White
- These vibrant flowers are closely tied to the rainy season and symbolize early summer’s quiet beauty.
Cicadas (Semi)
- As July approaches, the chorus of cicadas fills the air — a sound deeply embedded in Japanese summer memory.
- For many, the shrill cry of the cicadas marks the true start of midsummer.
- Children traditionally catch cicadas during summer vacation, making it a nostalgic rite of passage.
Personally, I still vividly remember chasing cicadas with my net during long summer holidays — one of the quintessential childhood experiences in Japan.
4. Japan’s Seasonal Sensitivity: More Than Just Weather
One reason Japan has such finely tuned seasonal markers is its cultural embrace of nature’s small changes:
- Seasonal foods (旬, shun) like watermelon, edamame, and unagi.
- Seasonal festivals, such as:
- Tanabata (Star Festival) in early July
- Obon in August
- Firework festivals (Hanabi taikai) throughout the summer months
- Seasonal greetings (暑中見舞い, summer postcards)
This heightened seasonal awareness is part of what makes Japan’s summer culture so rich, despite the often oppressive heat and humidity.
Summary
In Japan, the start of summer depends on which perspective you adopt:
| Perspective | Start of Summer |
|---|---|
| Traditional Calendar (Rikka) | Around May 5th |
| Meteorological Definition | Early to mid-June |
| Emotional & Cultural Sense | Late June to early July (fireflies, hydrangeas, cicadas) |
Japan’s sensitivity to nature’s transitions offers a beautifully layered way of experiencing the seasons — blending ancient calendars, modern science, and living traditions into everyday life.
This summer, wherever you are, take a moment to notice your own signs of seasonal change. Like the Japanese have done for centuries, you may discover unexpected beauty in the small, fleeting moments that mark the arrival of summer.
