1955 was an interesting spring in the Tri-State. Unusually warm weather occurred in February-March with a damaging hard freeze mid- to late-March.
15 days were in the 60s & 70s (some areas to 80) February 27-March 23 at Evansville. An Arctic Blast hit suddenly & dropped temps to a high of 21 with a low of 10 on March 26. There were three mornings in the single digits to teens over the Tri-State. This wiped out all budding & blooming vegetation, including blooming fruit trees
Vegetation re-foliated after this as the warmth returned with lots of 70s & 80s early to mid-April.
After a high of 79 on April 12 at Evansville after a morning low of 58, a squall line of storms moved through the Tri-State shortly before midnight April 12 & after midnight Apri 13.
A series of downbursts is evident in the storm reports from the time. Belches of intense apparent 70-85 mph wind gusts occurred west of Rockport, south of Philpot, east of Olney, southeast of Lamar (Spencer County) & north of Cisne in short 1-2 mile diameter damage paths.
This was part of a much larger outbreak of severe weather with upwards of 15 tornadoes.
On a side note, a downburst also hit near the Indianapolis Motor Speedway in Speedway, Indiana. Windows were blown out of apartment buildings, homes & a gas station, trees were toppled & a car was totaled. Other wind damage to trees occurred in the heart of Indianapolis.
This is how downbursts look in a line of storms (velocity data) from Sioux Falls, South Dakota area August 18, 2006: