An unspayed female cat rubs and yowls in spring. Why?

Answer: She may be in heat

She may be in heat ✓ — Correct! In estrus, an intact female may rub more, roll, demand attention, raise her hindquarters, and vocalize loudly. That can look like extra affection to humans, but biologically it is often a mating-receptive state, not simply a warmer personality.

She is charging by sound — Wrong. A loud cat is not charging a battery with sound, although it can feel that way at 3 a.m. When rubbing and yowling appear together in an unspayed female, heat is a much better first hypothesis.

She dislikes all warm weather — Wrong. Warm weather can change comfort and activity, but it does not explain the classic cluster of rubbing, yowling, rolling, and demanding contact. That cluster points more strongly toward estrus.