The thirteenth 節気 “sekki” division of the traditional Japanese calendar is:
‘first day of autumn’
The final “kō” microseason within this division is:
(ふかき きり まとう)
“fukaki kiri matō”
Thick fog descends
That makes 蒙霧升降 the thirty-ninth microseason of the year!
It typically lasts 18~22 August.
fog, mist, spray
Click here to learn more about this subseries
Image credit: Wikipedia entry on Pea-Soup Fog.