We had 88°F (31°C) here in Seattle today.
The National Weather Service issued a Heat Advisory for today and tomorrow for the Seattle area— with potential for temperatures in the mid-90s (35°C) on Wednesday.
These are also called night-shining clouds or polar mesospheric clouds. They are composed of ice crystals and form in the mesosphere, the atmospheric layer above the stratosphere, at extremely cold temperatures.
[Still image from a video clip posted by Skunkbayweather @Skunkbayweather on X]