What does sky with three lines under mean? NRK November 17, 2017 09:21 Updated Follow The weather symbol that shows a sky with three lines under means fog. Here is a complete list of the meaning of all the weather symbols at Yr. Related articles How does the weather visualisation work? Where can I find information about wind and wind direction? Where can I find sunrise and sunset times? Our collaborators Weather symbols at Yr Comments 0 comments Article is closed for comments.