Answer: It is very important to take the temperature in count while selecting an overhead line this is because of following reason
In summer, the temperature is high and the conductor will expand because of this sag will also increase. If the sag increases, firstly, the cleanest to ground clearance may not remain safe. Secondly, the swimming of conductor due to summer winds make calls short circuits.
In winter, the temperature is low and the line will contract. This will result in the reduction of sag and increase of tension in conductor. This may cause the conductor to break.