What if humans had a mating season?

First of all, only people who are between ages 20 and around 30 experience the breeding season. For some the season comes earlier, at 19, or later, even at 22. Most 'retire' from breeding in their late 20s. The rest of the population has a very low sex drive and practically zero fertility.

Women's periods are completely different. They are unnoticable from July to February. In March, a woman bleeds once and that means that for her the breeding season is starting. From then on, she is ovulating and able to get pregnant. That lasts until June. If she bleeds, that means that her fertile window is unsuccessfully over. During the fertile window, women's vaginas get tighter and produce more lubrication. Some women might even notice their breasts getting slightly bigger or starting to lactate. Outside of the season women have a very low sex drive and can hardly even achieve an orgasm.

Outside of the breeding season, men produce little semen and have a very low sex drive. In March, a man will cum in his sleep and that means that for him the breeding season is starting. From then on, his semen production and his sex drive will be hightened. Some even report a slight increase in dick length or girth. In June his sex drive and semen production may start to lower and that will signal the end of the breeding season for him.

People who are affected by the breeding season wear blue rings on their ring finger. For women it's not uncommon to wear a flower in their hair as well. Everyone dresses more slutty, trying to appear more attractive to possible mates. Sometimes people like to announce their start of the season by posting a picture of their wet or bloody underwear to social media.

The strength of breeding urges varies by person and by day - some days a person can feel almost nothing and on others they might start humping the floor in public. Everyone is easier to seduce and people find more people attractive. People have casual sex with strangers, knowing it might result in a pregnancy. Usually after sex with strangers people exchange at least phone numbers to keep in touch if the impregnation is successful. There are no pregnancy tests - the only way to know is if the woman starts showing or does not bleed in June. Public sex is not encouraged but it has been depenalized. People have a higher tolerance for perverts and random acts of spanking or groping aren't seen as rude.

While there are more single mothers than in real life, during impregnation people fall in love often and get married within weeks of meeting each other. Polyamory is more common than in real life. **** is not seen as morally wrong and does not affect the health of the fetus.