Northern lights in Japan tonight

Japan sits at the southern edge of where aurora can appear at all. Hokkaido, the northernmost main island, sits at roughly 42-45°N geographic latitude but only ~35-39° geomagnetic latitude - the latitude measured from Earth's magnetic poles, which is what actually decides where aurora reaches, and a low one. That puts it well outside the auroral oval under normal conditions. Aurora here needs a major geomagnetic storm. The Kp index, a global measure of geomagnetic activity from 0 (quiet) to 9 (extreme storm), needs to reach Kp 7-8 at best from Wakkanai in the far north, climbing to Kp 8-9 across the rest of the island, Hakodate in the south included. The main islands of Honshu, Shikoku and Kyushu are too far south to see aurora in all but the most extreme events on record.

This makes Japan a destination for storm-chasers rather than a place to plan a dedicated aurora trip around. Events are not nightly, or even weekly - they occur a handful of times a year during an active solar period, fewer in quieter years, and only when a coronal mass ejection or fast solar wind stream pushes Kp to 7 or above for several hours. The current solar maximum (2024-2026) has been one of the strongest in two decades and produced more aurora sightings from Hokkaido than at any point since Solar Cycle 23, including some visible as far south as Hakodate.

The practical approach is to treat Japan as a bonus rather than a target: visit Hokkaido for its own reasons - the national parks, the volcanic landscapes, the winter snow - and keep an eye on the space weather forecast during the trip. If a strong storm is called, Wakkanai, Rebun, Rishiri and the Okhotsk coast around Abashiri and Shiretoko are the places with the best chance of a clear, north-facing horizon.