Everything you need to know about the sticky sunshine
The climate of Okinawa can be extreme at times, and at other times mild and pleasant depending on what time of the year it is. The main island lies at around 26 degrees latitude and so has a subtropical climate. Although the tourist brochures advertise this place as an island paradise with beautiful sunny weather in a mild and warm climate, the reality of the weather here can be a bit different than that. The main island is often covered in clouds of some sort a majority of the time. If you enjoy clouds and cloud formations mixed in with your sunshine, then this is the place for you. In the summer, huge thunder clouds build up daily and can threaten rain at any time if the conditions are right.
Since there is so much water vapor in the air here, the island has exceptionally high levels of humidity at times. In the summer, this means incredible hot, sticky, and uncomfortable weather. To get an idea of how hot it can feel, the humidity averages around 80 to 85%. That means on a day where the temperatures are around 85 degrees Fahrenheit, 30 degrees Celsius, it can easily feel like around 37 degrees Celsius, 100 degrees Fahrenheit. When the actual temps go up to into the nineties Fahrenheit, thirties Celsius, the heat index can easily go up to 104 degrees Fahrenheit, 40 degrees Celsius or more. That means as a tourist, certain things are a must due to this mugginess. I always recommend carrying bottled water with you as there are a dearth of public water fountains. Fortunately there are plenty of convenience stores and vending machines around the cities where water and other drinks can be purchased. Muggy conditions can drain the body of water quickly as one constantly perspires, which can be uncomfortable, if not downright dangerous on a very hot day here. I also recommend that you carry a small hand towel with you at all times during the summer, as even a short walk on a humid day can leave one dripping with sweat.
If you intend to work out here during the summer whether it be for karate, running, or something else, be prepared for short, hot, and difficult workouts if you are not used to sultry conditions. If you are thinking of exercising inside to escape the sun, be prepared as well as there is a lack of air conditioning in the karate dojos and basketball gyms. Water or other sport drinks, sweat towels, and common sense are musts. Heat exhaustion and heat stroke are definite possibilities in summer here so take it easy. Humid weather can drain even the fittest athlete in a very short time. Showers are also a must after a workout as the constant humidity during the day will keep you and your workout clothes wet after exercising. Additionally, body odor quickly becomes a factor as well. A shower will help cool you off and your friends and family will thank you for it.
One more item worth noting is sunburn. Sunburns, especially in summer can happen rapidly and be very painful. In spite of all the clouds, the sun is strong here and will start burning the skin within 15 minutes of exposure. A strong sunscreen is recommended then for anyone planning to go outdoors for extended periods of time. This holds true for most of the year and one can easily get burned in fall and spring as well. So put that in with your water and towel also.
A great way to enjoy the summer heat is to go to the beaches during summer. The waters around the islands are downright warm ranging from upper 70s to low 80s F, upper 20s to around 30 C. This makes for great swimming and snorkeling temperatures while staying cool from the ambient air.
The transition to summer time is from May to June and it brings the rainy season. The rainy season is a monsoon that lasts for about a month and with it comes endless rain and humidity. When it rains in Okinawa and this is especially true of the rainy season, the rain comes down in buckets. It pours and literally there can be a couple of inches dumped in a couple of hours. This torrent of joy can go on all day long, and off and on for days at a time. Due to this, a good umbrella is recommended if you come to Okinawa during that time. Cheap ones can be purchased at any local Daiso stores which are the Japanese equivalent to dollar stores in the states.
Once the rainy season mercifully comes to an end, the real heat of summer kicks in until October. Thunderstorms are common in the summer and can literally drag on for hours sometimes. One particular species of lightning that happens here during the summer is heat lightning where there might not be any actual thunderclouds in the area, but lightning is happening nonetheless, seemingly coming from nowhere and without any sound. The final delight of summer worth mentioning is the typhoons which is the name given to hurricanes in the United States. Typhoons usually originate south of here in the Pacific and then either move west to the Philippines or move north to Taiwan, Okinawa or the mainland of Japan. These storms can come in multiples just like the hurricanes that originate off of the coast of Africa. They can range from almost nonexistent to down right terrifying. Typhoons are unpredictable and often times you will not know with 100% certainty how strong they will be until they are actually hitting the island. From my personal experience, best to err on the side of caution. That being said though, Okinawa is probably the best place on earth to ride out a typhoon safely. The buildings and infrastructure here are built to take & withstand category five hurricanes. There is often little property damage like what Americans are accustomed to in the states and the power and water supply is also not usually an issue when a typhoon hits. The best thing to do when a strong typhoon comes to Okinawa is stay in your hotel and ride it out safely. If the bus service is shut down in the main city of Naha, it means that generally most people are taking the day off and most places will be closed until the storm passes. If you are feeling foolhardy and courageous enough and feel like venturing out during a typhoon, there will probably be a few crazy taxi drivers out and about, ready to take you wherever you need or desire to go.
The fall, winter, and spring are all much shorter in comparison to the summer lasting about two months each. The winters can be cold and windy but also mild and uneventful compared to mainland Japan. The temperatures in the winter can drop down to 50 degrees Fahrenheit, 10 degrees Celsius which in itself is not bad, but add in the winds and the wind chill can easily make it feel a bit colder. Because of that, if you decide to visit in the winter, a good coat and maybe a light scarf is recommended for those cold days.
Fall and Spring are probably the best times of the year in Okinawa. The weather is usually tolerable and pleasant with clear and mild days in November and at the beginning of May around the Golden Week holiday. That being said, the weather at all times of the year can turn on a dime and go from pleasant to nasty in the space of just a few hours. So always be prepared and check the weather forecast before going out the door. The best way to do that is to go to the Japan Meteorological Agency abbreviated JMA at http://www.jma.go.jp/jma/indexe.html. Click on the Radar & Nowcasts (Precipitation, Thunder and Tornados) link for a radar shot of any and all precipitation or other weather events in the area. Clicking on that link will bring up a large radar map of Japan and all one needs to do is click on the island of Okinawa to get a close up view of what is going on in the skies weather-wise. Two other websites for Okinawa that I recommend in regards to typhoon forecasts are http://www.stripes.com/blogs/pacific-storm-tracker/pacific-storm-tracker-1.257110 and http://www.westernpacificweather.com/. Both of these sites will give you up to date information on any typhoons that are heading toward Japan.
With the right planning, there is decent weather all year round in Okinawa to be had for all, so come and enjoy!