HFT links use microwave frequencies. Water absorbs microwave radiation quite well (cf. microwave oven); as the water content (humidity) of air increases, so doe

HFT links use microwave frequencies. Water absorbs microwave radiation quite well (cf. microwave oven); as the water content (humidity) of air increases, so does microwave absorption. Conversely, signal power delivered to the receiver drops, and SNR decreases, making reception more difficult. Water should intuitively have a lower velocity factor, too, so waves might actually propagate more slowly in high humidity air compared to dry air.