Fog symbol
Three horizontal lines are the fog symbol on a weather map. Two lines are mist, and broken lines are fog in patches or shallow fog.
How to read it
Fog at the time of observation is the 40 to 49 group in the WMO’s present weather table, as reproduced by NOAA’s JetStream school and the University of British Columbia’s course chart. The three bars are fog that hides the sky, with no change in the past hour; the group’s other symbols add a mark for fog getting thinner or thicker, or for fog leaving rime ice. Mist, code 10, is two bars. The University of Wisconsin–Madison’s pilots’ course lists light fog and thick fog among its common symbols.
Also searched as: fog weather symbol, mist symbol, three horizontal lines, three lines weather symbol.
These pages describe what each symbol on a weather chart means. They are not forecasts or warnings: for those, the national weather service for the area is the source.
Shallow fog and patches
JetStream’s table has separate symbols for patches of shallow fog at the station, “not deeper than 6 feet on land”, and for fog in patches.
Look-alikes
An X in the station circle is not a weather symbol but the sky obscured mark, which JetStream uses when fog, dust or the like hides the sky. An orange dashed line on WPC’s charts is a Trough symbol, not fog.
Read next
- Next in Weather map symbolsCold front symbolA cold front: the leading edge of colder air pushing into warmer air. On a weather map it is a blue line with blue triangles, and the triangles point the way the front is moving.
- The same shape in Road signsRailroad crossing gateA red-and-white striped arm with red lights that lowers across the road at a railroad crossing. It comes down when a train is approaching and stays down until the train has cleared the crossing.
More weather map symbols
The same shape elsewhere
Browse symbols drawn with lines.
Sources
- JetStream Max: Surface Weather Plot Symbols, JetStream, the NWS online weather school, NOAA National Weather Service, Present Weather Symbols: codes 10-12, 40-49
- Present weather symbols (annotated chart), ATSC 113 course notes; descriptions abridged from the WMO code, University of British Columbia, Earth, Ocean and Atmospheric Sciences, Present weather, codes 10-12 and 40-49
- Weather for Pilots, Lesson 3: Station Model, Course content, University of Wisconsin–Madison, Department of Atmospheric and Oceanic Sciences, Weather Symbols
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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