Cool Biz: Japan's Seasonal Dress Code

A government-backed idea from the mid 2000s turned summer office dress into a nationwide habit of loosened collars and warmer thermostats.

Published October 18, 2026 at 11:09 PM JST | By Tokyo Paul

Quick answer: Cool Biz is a Japanese campaign, launched by the national government in 2005, that encourages lighter office clothing in summer so air conditioning can be set higher and energy saved. Men skip ties and jackets, and the idea is often paired with Warm Biz in winter, which promotes layers and lower heating.

What Cool Biz Actually Is

Cool Biz began as a summer program from Japan's Ministry of the Environment, introduced in 2005 under then Environment Minister Yuriko Koike. The idea was straightforward: if office workers dressed more lightly, buildings could run their air conditioning at a higher temperature, often around 28 degrees Celsius as a target, and use less electricity. The name is a catchy mix of English words, a style Japan often uses for campaigns. It encouraged shirtsleeves, open collars and no tie during the warmest months.

It was never a law, only an invitation, and companies and public offices decided how closely to follow it. Over time it became a familiar part of the Japanese summer calendar. Fashion retailers now run seasonal campaigns every spring, with displays of lightweight jackets, non-iron shirts and breathable trousers. Some brands design clothes specifically for commuters who walk long distances to stations in the heat, using stretch fabrics and moisture-wicking materials. This commercial support helped the idea spread beyond government offices to ordinary workplaces.

How It Changed the Office Look

Before Cool Biz, dark suits and ties were the default in most offices, even in the heat of July. After it caught on, many workplaces allowed short-sleeved shirts, polo shirts and lighter fabrics. Retailers responded with breathable suit materials, quick-dry shirts and cooling undershirts, and the clothing industry still markets items under the Cool Biz label each season. The change was gradual, and different industries took it up at different speeds. Government offices and large companies often led, while client-facing professions sometimes kept a more formal look.

In the years since, many employers have made smart-casual wear acceptable year-round, so Cool Biz now feels more like a baseline than a special event. In some years, companies extend the season earlier or later when temperatures run unusually high. Local governments also publish guidance for their own staff. Because Japan stretches over a long north to south range, a company in Hokkaido may start much later than one in Okinawa, and each uses sensible local judgment rather than a fixed national date.

Seasonal Timing

Cool Biz typically runs from the start of the warm season, often around May or June, through to about September or October. Exact dates differ by organization, and local weather affects how long it lasts. Some companies announce start and end dates in an internal notice, while others leave it to individual judgment. If you are visiting an office in summer, you can usually assume lighter dress is acceptable. Still, a first meeting with a client may call for a jacket, even if you do not wear it all day.

Carry one in a bag and put it on if the situation seems formal. This approach shows respect without making you overheat on the train. Popular Warm Biz items include thin heat-generating undershirts, which are widely sold in department stores and convenience stores, as well as thick socks, knee blankets used at desks and fingerless gloves. These items are practical, affordable and easy to find, so a visitor caught unprepared by a chilly office can pick something up quickly.

Warm Biz for Winter

Warm Biz is the winter counterpart, introduced a little later. It encourages layering, such as warm undershirts, cardigans, vests and scarves, so heating can be kept at a lower level, often around 20 degrees Celsius as a guide. Clothing makers promote heat-retaining base layers, and many people wear them under regular work clothes. Warm Biz has a gentle, practical feel. Instead of raising the thermostat, you add a layer. In shops and department stores you will see sections devoted to thermal wear in autumn.

For visitors, this means offices and shops may feel cooler than expected in winter, so a light sweater or cardigan is helpful indoors. If you tend to feel warm, look for pocket-sized cooling products sold in summer, including sheets that refresh the skin and neck wraps that can be chilled. Pharmacies and variety shops stock these in large displays. They are inexpensive and a good way to follow the local approach to coping with seasonal heat.

Practical Tips for Visitors

Indoor temperatures during Cool Biz can seem warm to those who expect strong air conditioning. Trains, in contrast, may run cold on certain cars, and many lines have designated weak-air-conditioning cars for people sensitive to the chill. A thin cardigan or scarf covers the difference between outdoor heat and indoor cool. Pack breathable clothes in cotton or linen, a compact towel for wiping sweat and a small folding fan or handheld one, which many people carry in summer.

Sunscreen and a hat or parasol are common. Stay hydrated, as vending machines and convenience stores are everywhere. These small habits make a humid day more comfortable. Grooming becomes more visible when jackets come off. Pay attention to ironed sleeves, tidy hair and clean fingernails. Carry a small cloth for wiping your forehead instead of using your sleeve, and keep a spare shirt if you will be walking for long distances before a meeting. These habits help you look composed even when conditions are warm.

Etiquette Around Casual Summer Dress

Loosened dress does not mean careless. Shirts should be clean and pressed, shoes polished, and clothing free of strong odors. Sleeveless tops and shorts are rarely suitable for business settings. Sandals can look too informal for an office, though some workplaces permit them. Take cues from your host. If everyone in a meeting wears a jacket, follow suit. If they are in shirtsleeves, you can relax too. When unsure, dress slightly more formally than expected, and let the other person invite you to remove a layer.

A friendly comment like asking whether it is fine to take off your jacket is usually welcomed with a smile. For visitors, the practical lesson is that Japan tends to approach seasonal comfort through shared habits instead of strict rules. People adjust their clothes together, shops announce the changes in their displays, and offices send around friendly reminders. Noticing these small cues is a pleasant way to understand how the seasons shape daily routines.

Why It Stuck

Cool Biz stuck partly because it solved an obvious comfort problem and partly because it gave everyone permission to change. When the government and large companies endorsed lighter dress, individuals no longer needed to feel they stood out. The campaign also fit a broader culture of energy awareness in Japan. It continues to evolve with workplace trends. Remote work and relaxed standards have loosened expectations further.

Even so, the Cool Biz label survives in advertising, store displays and office announcements each summer, and it remains a useful clue for visitors trying to understand how seasons shape daily life in Japan. Seasonal clothing campaigns by shops and brands keep the idea fresh from year to year. Travelling in summer, you will see its effects in offices, banks and department stores, where staff wear lighter uniforms.

Frequently Asked Questions

When does Cool Biz start and end?

There is no single legal date. Many organizations treat roughly May or June through September or October as the Cool Biz season, depending on the weather. Individual employers announce their own timing, so check with your host if you are attending a business visit.

Is a tie still needed in summer meetings?

Often not, but it depends on the setting. Cool Biz allows open collars and no tie, yet first meetings with senior clients can be more formal. Carry a tie and jacket in your bag and put them on if the situation seems to call for it.

What is Warm Biz?

Warm Biz is the winter companion to Cool Biz. It encourages layers such as thermal undershirts and cardigans so offices can keep heating lower and save energy. Expect indoor spaces to be cool in winter and bring a light layer to stay comfortable.

Keep Exploring

More guides from Tokyo Paul: Japanese Dress Codes: Business, Casual and Formal Events, Kuuki wo Yomu: Reading the Air in Japan and Gaman: Patience and Perseverance in Japanese Culture.