Artist's commentary
Touhou 4-panel #1310 Hot Springs!
The ability to cause hot springs to boil up.
[Survey: What bath temperature do you prefer?]
• 37˚C or less
• 38˚C
• 40˚C
• 42˚C
• More than that
That's ≤98.6˚F, 100.4˚F, 104˚F, and 107.6˚F, respectively.