Warmth

There are many ways to make nouns out of adjectives in English. For example:

This is a boring movie. The boringness of it makes me tired.

Adding "ness" works often, but not always. For the weather, we turn adjectives into nouns like this:

It's hot. The heat is melting me.
It's warm today. This warmth is quite comfortable.
There's a cool breeze outside today. The coolness of it is very refreshing.
It's too cold. I hate the cold.

Spring is starting soon - so let's all enjoy the newfound warmth!