The global decline in sperm quality remains poorly understood. As climate change intensifies, extreme temperatures are increasingly recognized as potential threats to reproductive health. This study examined the association between ambient temperature and sperm quality, focusing on subgroups with normal and abnormal sperm parameters.

Sperm quality data from Soroka University Medical Center fertility clinics (May 2009–March 2023) were linked to ambient temperatures recorded up to 90 days before sample collection from nearby monitoring stations. Maximum summer temperatures ranged from 25.3 °C to 46.4 °C, and winter minimums from 0.1 °C to 24.5 °C. Directed Acyclic Graphs informed confounder selection in Generalized Additive Mixed Models and Distributed Lag Models. Mixed-Effect Negative Binomial Regressions compared sperm quality in the highest vs. lowest seasonal temperature quartiles.

Exposure to low winter temperatures was significantly associated with reduced sperm motility, showing a 5.5% decrease (p < 0.001). Subgroup analyses indicated stronger effects among Jewish men and older men, with decreases of 3.6%–6.5%. Extreme summer heat had minimal effects overall, though men of lower socioeconomic status exhibited a borderline significant 5.9% motility reduction.

Extreme cold but not heat was negatively associated with sperm motility, suggesting potential behavioral mitigation to summer heat in desert climates. With increasing climate variability, these findings highlight ambient temperature as a potential environmental determinant of semen quality and underscore the need for further research among vulnerable subgroups, including men with abnormal sperm quality, smokers, and those with chronic illnesses.