Lightning and stormy weather all contribute to electromagnetic interference. In situations where your line stats (Attenuation and SnR) are good then the weather will have a minimal effect on the line. In my case it causes small amounts of packet loss here and there. If you line is just barely reaching its target speed then you will run in too trouble during rainy weather. Electromagnetic interference will result in signal quality loss, meaning the SnR value on your router will be affected. If you are already running with an SnR below 7 or 8 ish then you will more than likely lose your connection all together. Given, all of this can be avoided if cabling was better isolated and sealed to prevent interference but hey, its Telkom and they just moered the cable in the mud somewhere.