Due to the size and width of wedge tornadoes, they are thought of as the largest and most menacing tornado type. It is so broad that at first glance it's not recognized as being a tornado. The base, or part of the storm that touches the ground, of a wedge tornado can be a mile or more wide, and often looks like low-hanging dark clouds to passersby. These "fat" storms often bear the lion's share of blame among tornado survivors, because they seem to strike without warning.
As if they weren't already difficult to see, wedges can also be "rain-wrapped." When this occurs, curtains of nearby rainfall encircle the tornado funnel, veiling the twister and further lowering its visibility.
https://www.thoughtco.com/wedge-tornadoes-natures-largest-twisters-4126783
Very good comment to inform people how these massive tornadoes can fool people. It’s hypothesized that this is how the Tri-State outbreak in 1925 killed so many.
Thomas Grazulis in “Significant Tornadoes” said the “normally weather-wise farmers knew their storms” but this was only a darkening on the horizon. Moving at 70 mph snuck up on them fast.