Japan Meteorological Corporation (Headquarters: Osaka, Japan; President: Masanori Suzuki; hereinafter “JMC”) is providing our “Sunset Information” and “Rainbow Information” on the signage displays at Expo 2025 to inform visitors possibilities of seeing sunsets and rainbows there.
The beautiful sunsets seen from the Expo site have become a hot topic of conversation on social networking services, and have impressed a lot of expo visitors. We have conducted a survey on the occurrence of sunsets since the opening day of the Expo, verified the number of days that sunsets were seen and the accuracy of the sunset information provided by JMC, and published the results.

The magnificent sunsets from the Expo site attract many visitors. In order to provide visitors with a special experience, JMC is providing the accuracy of sunsets and rainbows when they are visible in the vicinity of the Expo site on seventeen signage screens. Our “Sunset Information” and “Rainbow Information” were originally developed by JMC, and are broadcast daily in both Japanese and English.

The “Sunset Information” provided on the signage displays at the Expo site is also available on the official website of JMC. When you are in a place where it is difficult to notice the sunset, such as inside a building, the website can support you to make a plan to enjoy the beautiful scenery of the Expo.

JMC has verified the accuracy of the “Sunset Information” for 72 days from April 13 to June 23, 2025. For this verification, we took photos of the Yumeshima area every day from our headquarters in Osaka City to investigate the occurrence of sunsets.
During these 72 days, the sunset was actually visible for 36 days. This means that sunset was visible from the Expo site for half of the period.

JMC forecasts the possibilities of seeing sunsets as our sunset index on three levels: “highly likely to see a sunset,” “likely to see a sunset,” and "less likely to see a sunset”.
On the signage displays at the Expo site, “highly likely to see a sunset” and “likely to see a sunset” are indicated as "Sunset Today!”, and "less likely to see a sunset” is indicated as "No Sunset Today!”

In this verification, we evaluated the accuracy of the “Sunset Information” based on its occurrence by photographing the sunset.
The accuracy rate of the “Sunset Information” during the period was 73%.
Moreover, the possibility of seeing a sunset when the sunset index is “likely to be visible” is 91%. We confirmed the high accuracy of our forecast.

Generally speaking, sunsets are more visible when the following conditions are met.
- There are appropriate amounts of dust, water vapor, and other particulates in the air.
- Few clouds in the western sky at sunset time.

When these conditions are met, sunlight is scattered in the atmosphere, resulting in a beautiful red-orange sunset.

As well as our “Sunset Information”, we are providing our Rainbow Information” based on our own technology. We are forecasting weather conditions under which rainbows are likely to occur and provide visitors with the opportunity to encounter them. We have been able to build on our achievements in a variety of situations, such as the use of our rainbow forecast on the sightseeing website of Shiga Prefecture.

Especially around summer, you have a good chance when the sun is low in the morning or evening and rain clouds pass nearby when the sun is shining. Rainbows are visible on the opposite side of the sun, so let’s turn your back to the sun and look over toward the rain clouds!

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