Abstract: The objective of the present study was to determine the relationship between the incidence of anestrus post calving cows and the ambient temperature, months and calving seasons. This study was carried out on an imported dairy herd. The herd comprises of Holstein, Friesian crossbreeds. The results of the study indicated that a total percentage 49.36% of the cows suffering from delayed reestablishment of estrus till day 45 post calving while 33.19% were suffering from delayed estrus reestablishment till day 65 post calving. Meanwhile, the results of the study revealed an inverse relationship between the ambient temperature and the percentage of cows that showed a delayed in re-establishment of post calving estrus. According to seasonal classification, a higher percentage (66.3 and 47.28%) of anestrus cows post calving till day 45 and 65 post calving subsequently were recorded during winter whereas lower percentage (22.77 and 1.98%) subsequently were recorded during summer. The result of clinical examination (rectal palpation of ovaries) of 241 cows failed to exhibit estrus symptoms revealed that 64.73% of these cows were with group inactive ovaries (without corpus luteum) whereas 35.27% of these cows were with active ovaries (with corpora lutea), this of cows is recognized as cows with silent and unobserved estrus, statistical analysis of the data indicated that there is no relationship between the unobserved estrus (or silent estrus) with the ambient temperature. The results also showed that high percentage of anestrus post calving cows with inactive ovaries were recorded during winter and autumn (73.11 and 71.78%) subsequently whereas high percentage of anestrus post calving cows with active ovaries were recorded during summer.