A University of Washington study showed that the number of couples who file for divorce in March and August are disproportionately higher than any other months. The pattern emerged after reviewing divorce filings in the state of Washington over a 15 year period. The same pattern was then found in studies of Ohio, Minnesota, Florida and Arizona thus strengthening the results and begging the question of why.
Researchers hypothesize the seasonal divorce trend has to do with how unhappy spouses may feel during vacation periods and file for divorce when the vacation period fails to save the marriage. Julie Brine is an Associate Sociology Professor at the University of Washington and was one of the researchers conducting the study. She believes there is a cultural basis for the finding describing the ‘winter and summer holidays’ as ‘culturally sacred times for families when filing for divorce is considered inappropriate, even taboo.’ Many unhappy spouses also optimistically view the winter and summer holidays as symbolic of a chance for renewal. “People are discontent with their marriages, and they look at vacations as an opportunity for one last chance," Brine says. She also hypothesizes people go on these trips hoping for reconciliation but are disappointed when it doesn't happen. The data suggests the summer and winter vacations tend to expose irreconcilable differences the unhappy spouse are no longer willing to live with.
Although the optimism cycle described by Brine accounts for some of the increased Spring and late Summer filings, it does not account for all of them. Some unhappy spouses have a more pessimistic view of the summer and winter holidays and consider them a deadline to divorce. Therefore, it is not uncommon for unhappily married couples to file for divorce in August hoping their decisions will be finalized by the winter holidays of Thanksgiving, Christmas and New Years. A study conducted in England found a spike of divorces beginning in August due to this trend, especially among parents with children who want minimal conflict during such a culturally sacred time of year.
In conclusion, more couples file for divorce after winter and summer vacations because they're just not happy together anymore or disappointed by their failed reconciliation attempt. The timing of the divorce is likely influenced by the culture at large but has implications on a couple's children as well.
https://www.washington.edu/news/2016/08/21/is-divorce-seasonal-uw-research-shows-biannual-spike-in-divorce-filings/