During a large explosion the air is pushed away from the center of the explosion and compressed into a supersonic shock wave, which creates the loud sound we hear from the blast. Immediately behind the shock wave an area forms of low pressure and temperature. If the explosion is sufficiently strong and occurs in a humid environment, the temperature of the air behind the shock wave can briefly drop below the dew point causing water molecules to rapidly condense into water droplets forming a cloud. In the first atomic bomb tests carried out in the Bikini Atoll in 1946 (Operation Crossroads), these clouds were called Wilson Clouds. They were named after the Scottish physicist Charles Thomson Rees Wilson who won a Nobel Prize (shared with the American physicist Arthur Compton) in 1927 for the development of the cloud chamber which allowed the visualization of radioactivity.
In the video below, an atomic bomb named “Baker” is exploded underwater next to unmanned ships to test its power. You can see the large Wilson cloud begin to develop around the huge central column of water 9 seconds into the video.
Today Wilson clouds are called “condensation clouds”. Condensation clouds can also form during far weaker explosions under the right conditions such as the one that rocked the port of Beirut in 2020. The white condensation cloud begins to develop 11 seconds into the video. It envelops the central red-colored explosion cloud and then quickly dissipates.
However, man-made condensation clouds are not only formed during explosions. Anything capable of generating a supersonic shock wave such as a fighter jet can generate such a cloud, which is this case is called a vapor cone.