A cat's heat cycle, specifically the estrus phase when she is "in heat," typically lasts about 3 to 14 days, with an average duration of around one week. During this time, the cat exhibits behavioral changes such as increased vocalization, affection, and restlessness, indicating receptiveness to mating

. The entire estrous cycle, including phases before and after estrus, can span roughly three weeks (about 21 days). If the cat does not mate and ovulate, she enters an interestrus phase lasting about 1 to 3 weeks before starting another heat cycle

. If she mates and ovulates, the cycle pauses for pregnancy or pseudopregnancy periods. Unspayed female cats can go into heat repeatedly every 2 to 3 weeks during their breeding season, which usually lasts from early spring to late autumn in temperate regions. Indoor cats or those in warmer climates may cycle year-round

. In summary:

• Estrus ("in heat") phase: about 3–14 days, averaging 7 days
• Full cycle length (including interestrus): about 3 weeks
• Recurrence: every 2–3 weeks if not mated
• Breeding season: typically February to October, but year-round possible indoors or in warm climates

This frequent cycling can continue indefinitely unless the cat is spayed