Cats in heat typically remain in the estrus phase-the period when they are receptive to mating and show heat behaviors-for about 3 to 14 days, with an average duration of around 7 days. This phase is characterized by vocalization, restlessness, and affectionate behavior

. If the cat does not mate during this period, she usually goes out of heat for a short interval (interestrus) lasting about 2 to 19 days before returning to heat again. This cycle can repeat every 2 to 3 weeks during the breeding season, which generally spans from late winter or early spring through autumn in many regions

. In summary:

• Heat (estrus) lasts about 3 to 14 days, averaging 7 days.
• If unmated, cats cycle back into heat every 2 to 3 weeks.
• The breeding season typically lasts 7 to 9 months, with multiple heat cycles possible.
• Indoor cats or those in consistent light environments may cycle year-round

Therefore, a cat in heat may exhibit heat behaviors for about a week at a time, recurring frequently throughout the breeding season unless she mates or is spayed.