in heat

Idioms  

1. In a state of sexual excitement immediately preceding ovulation. For example, Our cat's in heat so we have to keep her inside. This expression applies to most female mammals and indicates the period when the animal is fertile and most receptive to mating. [Mid-1700s]

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Example Sentences

Ground-level ozone, often called “smog,” is a corrosive gas that forms when pollution from vehicles and other sources reacts in heat and sunlight.

From Los Angeles Times • Apr. 22, 2026

Unlike internal combustion engines, which require a large temperature gap to operate efficiently, Stirling engines can run on much smaller differences in heat.

From Science Daily • Feb. 27, 2026

The Celtic powerbrokers, who have been engulfed in heat from the fans, knew what they were doing with this one.

From BBC • Nov. 2, 2025

An extra layer of low-moisture cheese between dough and sauce helps lock in heat for travel.

From The Wall Street Journal • Oct. 8, 2025

I was swimming in heat, bathed in heat, swaddled in it.

From "A Walk in the Woods" by Bill Bryson