[kobalsky]

Long time ago I had a 10km 2.4ghz wifi link with directional antennas, it worked very well but the throughtput improved with rain.

Directional antenas are far from directional, they pick noise from everywhere.

In my opinion rain reduces that noise, and if the point to point has more than enough signal margin to keep operating at full speed, it ends up improving the link.

Something like horse blinders.