Visitors to the Tateyama Kurobe Alpine Route in Toyama Prefecture observed a rare "red snow" phenomenon during the summer mountain opening on July 2, 2026 [1].
The event is significant because the intensity and scale of the coloration are unusual for the region. Local officials said that such deep red hues have not been recorded in recent years [1].
The phenomenon occurred at Murodo, located at an altitude of 2,450 meters [1]. The red color is caused by snow-ice algae, which possess a red pigment. These algae proliferate during the residual snow period in June, fueled by sunlight and meltwater, which stains the snow surface [1].
"I was surprised. I wondered why it was turning red," said a tourist from Niigata [1].
Jun Kinjo, director of the Tateyama Nature Conservation Center, said the scale and depth of the color are notable, and said there are no recent records of the snow appearing this red [1].
The red snow is a seasonal spectacle that is typically visible only until mid-July [1]. The timing coincides with the transition from the heavy winter snowpacks to the summer hiking season on the Alpine Route.
Environmental factors, including the specific temperature of the meltwater and the intensity of the summer sun, dictate the proliferation of the algae. While the sight is visually striking for tourists, it is a biological process tied to the specific ecosystem of the high-altitude Japanese Alps [1].
“The red color is caused by snow-ice algae, which possess a red pigment.”
The appearance of 'red snow,' often referred to globally as watermelon snow, serves as a visible indicator of biological activity within the cryosphere. Because the intensity of this year's algae bloom is reportedly higher than in recent years, it may reflect specific shifts in meltwater temperatures or sunlight exposure at high altitudes, providing a data point for those monitoring the Tateyama ecosystem's response to seasonal changes.
