Why did the ancient Romans wear clothes made out of wool when it was hot?

Answer 1

They didn't all the time, they wore woollen clothes in the winter months, when it was cold but not all the time-others were imported; silk (was very expensive), cotton was also available, leather was used for some clothes as well as shoes. Many fabrics were made in looms.

Cotton and silk were imported from Egypt and China respectively and were rare and very expensive. Linen (also imported from Egypt) was more expensive than cotton. Flax growing requires a lot of taking care of. Threading was difficult and time consuming. Weaving was also difficult. The thread was rigid and difficult to weave without breaking it.

Imported materials were expensive and exclusive for the very rich. Leather was used only for the clothing of some soldiers. Most people wore wool all year round. Wool is a warm material when it comes in thick fabric. Thin wool fabric is quite cool. Moreover, the night in the Mediterranean can be quite cold in the Autumn as well and wool could provide a warmer evening cloth, too.

Wool was abundantly available in Italy and was easy to produce. Therefore, it provided affordable and easily available material.