3 October 2017 | InsideTowers.com

So how does the rain detection via towers work?

Because rain weakens electromagnetic signals and many mobile-phone towers, especially in remote areas, use microwaves to communicate; a dip in the strength of those microwaves could reveal the presence of rain.

Link To Article

https://phys.org/news/2013-02-attenuation-cell-towers-rainfall.html