SPC Stats

Path length: 31.8 miles

Width:  1000 yards

Fatalities:  0

Injuries:  10

Rating:  F4

County:  Marathon

Two tornadoes were confirmed on August 31, 1977.  The strongest traveled through a good part of Marathon County, WI.  There is a discrepancy in the rating.  The SPC and NCDC databases list a rating of F4 with this tornado.  In a Google search, I ran across a 1970s Tornado / Waterspout Guide from the NWS Green Bay.  They list this tornado with a rating of F3.  Thomas Grazulis in Significant Tornadoes also has this tornado listed as F3.  He mentioned “Near-F4” damage at 15 homes at Rib Mountain.  Regardless, this was a significant tornado that caused a tremendous amount of damage. Total losses per Storm Data of $3,5000,000+ in Marathon County.

There is also a big discrepancy in the path length.  All sources agree the path remained in Marathon County.  The above tornado/waterspout guide states the path was 27 miles.  The SPC and NCDC database have a length of 31.8 miles.  Storm Data and Grazulis list the path length at 45 miles.

This tornado moved at tree-top level at the start of its path.  Near Marathon City there were barns destroyed  and extensive damage to the Ginseng corp. Most widespread damage seemed to be at Rib Mountain.  With 45 homes destroyed/severely damaged.  In Wausau, there was damage on the ground and at tree-top level.  

There were no fatalities and 10 injuries.

Storm Data Entry

On the evening of August 31, a devastating tornado “spun out” a 45 miles path of destruction across Marathon County.  The first sightings of the funnel came form 7 miles southwest of Fenwood.  The funnel base was described as reaching tree top levels as it downed barns in the area.  The next sightings were near Marathon City where more barns were destroyed and extensive damage to Ginseng (root) crops.  The funnels’ first touchdown was in the town of Rib Mountain at 740pm where 15 homes were demolished and 30 others severely damaged.  The storm then moved into southwest Wausau damaging a mill and lumber yard.  As the funnel moved across the southern end of Wausau, local observers described it as “dancing” at tree top levels.  Brief touch-downs occurred at Grand Avenue and at Tenth and Manson Streets.  The storm moved out of the Wausau City limits and touched down on McIntosh Street.  The funnel then lifted and moved eastward touching down for a final time on Linden Street.  Barns and sheds were destroyed on Linden.  The funnel reported lifted and dissipated after its Linden Street touchdown.  Heavy damage occurred on 20th Street.

Damage occurred to 60 farms for an estimated loss of $1,036,000.  In Wausau, business losses were put at $300,000, automobile damage at $78,000 and damaged homes at $1,570,000.  Total loses in Marathon County were estimated in excess of $3,500,000.

Tornado Path

Click Map To Enlarge

SPC coordinates:  Start: 44.78 / -90.10   End:  44.97 / -89.50      

Note:  Exact tornado path may not be straight and/or continuous.

Newspaper Clippings


We gathered information for this event from the SPC & NCDC Databases, the August 1977 Storm Data Publication and Thomas Grazulis in Significant Tornadoes and found the following differences:

Path Length:

  • SPC/NCDC have a 31.8 mile path length.
  • Grazulis and Storm Data have a length at 45 miles.

Max Width:

  • Grazulis has a width of 400 yards.
  • Remaining sources list the width at 1000 yards.


  • Grazulis has a rating of F3.
  • NWS Green Bay has a rating of F3 in their 1970s Tornado/Waterspout Guide
  • SPC/NCDC have an F4 rating.


      The Storm Prediction Center

      NCDC Storm Events Database

      August 1977 Storm Data Publication

      1970s Tornado / Waterspout Guide via NWS Green Bay


      Grazulis, Thomas P. (1993). Significant Tornadoes 1680-1991: A Chronology and Analysis of Events. St. Johnsbury, VT: The Tornado Project of Environmental Films. Page 1198.

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