It can have some effect but at the distances aimed (max 3km for a high reliability, high Tx power 80 GHz link) it doesn't affect much. A link that is a nominal -34 RSL on a clear sunny day might drop to -36.5 as a result of building sway (such as if one end is on top of a 60 floor tower). Weather is the main issue not heat expansion/contraction or sway.