Will the downburst form rain?

The downburst itself does not form rain. Mainly brings windy weather.

There are two main causes of "downburst": one is that a large number of water droplets fall in cumulonimbus clouds and squeeze the air downward; Secondly, when falling water droplets or hail pass through the dry air layer, it will evaporate or sublimate sharply, taking away the heat in the remaining water droplets or hail, increasing the density and accelerating the air drop.