Summer and Infidelity: What the Research Actually Says
By Mark Ryan, BACP Accredited Psychotherapist and NCPS Accredited Relationship Therapist
You may be reading this because your partner has gone away on a work trip, a stag or hen weekend, a family holiday alone, or because something quieter than that has prompted a Google search you weren't expecting to make. The internet is full of confident claims about summer affairs, peak infidelity months, and the seasonal patterns of cheating. Much of it is overstated, and some of it cannot be traced to any source at all.
This piece is about what the research can and cannot tell us, and what to do with that if it is relevant to you. It is written by a London relationship therapist who works with couples after infidelity, and the aim is to be useful rather than alarming. The honest picture is more measured than the headlines suggest.
If you are reading this in a state of acute worry, please know that the piece will not catastrophise. It will also not minimise. Both extremes are common in writing on this subject, and neither is useful to a reader who is trying to work something out.
In brief
The figures about peak months for affairs that circulate online rarely come with a source you can check, and I have not found a precise one I can stand behind.
How often infidelity is reported depends heavily on how people are asked.
What the research links with infidelity is mostly about the people and the relationship, and not the calendar.
There is research on holidays and relationships. A study of divorce filings found peaks in March and August, which fits the idea that holidays can surface what is already there.
If you are worried, there are better things to do than checking a phone. If you already know something has happened, there is a workable path forward.
What circulates online, and why to be careful
Most of what circulates online about summer infidelity comes from private investigation firms, dating and affair sites, and tabloid pieces that recycle the same statistics every June. The figures sound precise (affairs are a particular percentage more common in summer, or August is the peak month for cheating), but they rarely come with a source you can check, and they are often produced by businesses that profit from people's worry. I would treat them with caution.
I would also be cautious about anyone, including me, who states with confidence that infidelity peaks in a particular season. A seasonal pattern is plausible, and I explain below why. But I have not been able to confirm a precise figure for any seasonal effect on infidelity from a source I can stand behind, so I am not going to give you one. What I can do is tell you what the better evidence shows.
What the research can tell us
How common is infidelity, and why do the figures differ so much?
Figures for how common infidelity is vary a good deal depending on how it is defined and who is asked, and the method of asking matters more than most people expect. In a national survey of 4,884 married women in the United States, the annual prevalence of sexual infidelity was 1.08 per cent when the question was asked in a face to face interview, and 6.13 per cent when women answered by computer. The authors concluded that this underlines the importance of assessing infidelity with methods that reduce the influence of social desirability (Whisman & Snyder, 2007). That is one study of one group, so it cannot tell us how common infidelity is in general. It does suggest that what people say aloud and what they will say privately can differ, and that any single percentage should be read with the method in mind.
A different study, of heterosexual couples, found that almost a quarter of the men (23.2 per cent) and 19.2 per cent of the women said they had cheated during their current relationship, meaning they had engaged in sexual interactions with someone other than their partner that could jeopardise or hurt the relationship (Mark et al., 2011). That is a meaningful minority and not a majority. The two figures measure different things, over different periods, in different groups, which is a good illustration of why headline percentages online tend to mislead.
What is linked with infidelity?
The same study of heterosexual couples looked at what predicted infidelity. It found that sexual personality characteristics were more relevant than demographic factors such as marital status and religiosity, for both men and women. For women, low relationship happiness and low compatibility in sexual attitudes and values also predicted infidelity (Mark et al., 2011). A broader review of the research on infidelity organised the evidence under topics including attitudes, prevalence, types of infidelity, gender, issues in the primary relationship, individual issues, attachment, and opportunity (Blow & Hartnett, 2005). Opportunity is on that list, which is part of why the idea that travel might matter is plausible, but it sits alongside personal and relational factors and does not replace them.
The point worth taking from this is that infidelity was linked more with personal and relational factors than with what the calendar says or what stage of life someone is at. It does not give you a way of predicting whether your partner is more or less likely to be unfaithful. It describes groups, and a group is not a person.
What do we know about holidays and relationships?
There is some research on holidays and relationships, though it is about divorce and not about infidelity. Sociologists at the University of Washington analysed divorce filings in counties across Washington State between 2001 and 2015 and found that they peaked in March and August, the periods following the winter and summer holidays. The researchers believe the pattern reflects the disillusionment unhappy spouses feel when holidays do not live up to expectations (Brines & Serafini, 2016). I want to be careful about how far this goes. It was a paper presented at a conference, not yet a published journal article that I could read, it covers one US state, and it concerns when people file for divorce and not when affairs happen. But it fits something I see often, which is that a holiday can surface what was already there. I have written separately about why couples argue more on holiday and about what to do when summer exposes the cracks.
Why summer might matter
If there is a summer effect on infidelity, there are several reasons it could exist, and the combination probably matters more than any one of them. These are reasonable explanations drawn from how circumstances shape behaviour. They are not findings from a study, and I offer them as ways of thinking about it.
Travel and physical distance
A partner who is away from home is also away from the routines and visibility that ordinary life imposes. Detection is harder, opportunity is greater, and the friction that normally sits between an impulse and an action is reduced. This is not a moral observation. It is a description of how circumstances shape behaviour, and circumstances change in summer.
The dissolution of routine
Most couples function in long relationships partly through shared routine: shared meals, shared evenings, shared knowledge of where the other is and what they are doing. Summer holidays, travel, school holidays and the redistribution of who is where all disrupt that quiet structure. The loss of routine does not cause infidelity. It does change the environment in which choices are made.
Difficult holidays that surface what was already there
Some affairs do not begin in summer. They become visible in summer, because a difficult holiday surfaces what was already there. A couple returns from a trip that exposed long running disconnection, and one partner acts on what they had been considering for months. In my experience this is closer to what often happens than the stereotype of the spontaneous affair. Summer is rarely the cause. It is more often the context in which something already in motion arrives at the surface. If the quiet version of this is what you are noticing, the summer slump and having nothing left to say to each other may be closer to what is going on.
Alcohol and group social settings
Stag weekends, hen parties, summer weddings, work conferences, group holidays and large gatherings all concentrate in summer. They combine alcohol, group dynamics and removal from everyday accountability, in an atmosphere some people find harder to navigate than others. Most people in those settings are not unfaithful. Some are.
What none of this tells you
It is worth being clear about what is not being claimed, because misreading this kind of information causes real damage to relationships that did not need it.
Nothing here tells you that most affairs happen in summer. Even if there is a seasonal bump, infidelity happens at every time of year, and a partner away on a work trip in February is not protected by the calendar.
Nothing here tells you that a partner travelling alone is a meaningful risk. The number of people who travel alone in summer without being unfaithful is far larger than the number who are. Reading this information as a reason to be suspicious of any partner on any solo trip is reading it badly.
And nothing here lets you predict whether your partner specifically is more or less likely to be unfaithful. Population figures cannot do that.
Most of what circulates online about summer infidelity is louder than it is accurate.
What you can do if this is on your mind
If the topic is on your mind because of a specific concern about your partner, there are a few things worth knowing about what helps and what does not. This section is written for a reader who is in real, low grade worry rather than acute crisis. If you are already certain something has happened, the next section addresses that directly.
Notice what you are really worried about
People who search for summer infidelity at 11pm are usually carrying one of two distinct worries. The first is about their specific partner in a specific situation: the work trip next week, the weekend away with friends, the visit to a particular person. The second is more diffuse, about the state of the relationship itself, and the worry has attached itself to a summer event as a way of finding shape. These two worries call for different responses. The first might benefit from an honest conversation with your partner about your concerns. The second is rarely solved by a single conversation about a single trip, because what is worrying you is the relationship, not the trip.
Surveillance rarely produces the reassurance it promises
Checking a partner's phone, tracking their location, looking at receipts, reading their messages. These activities sometimes produce information, but in my experience they almost always produce damage to the relationship that is doing the checking, regardless of what they find. If you have genuine reason to believe something is wrong, the more useful path is usually to talk directly to your partner about what you are noticing. If you have no reason beyond a general worry, surveillance tends to confirm the anxious version of your mind without protecting against anything real.
Talking to your partner is harder and more useful
The honest conversation about worry is the difficult one. Most readers will already have considered it and decided it is too risky, too embarrassing, or too likely to be dismissed. The version of it that lands well is not an accusation. It is more like: 'I am noticing some worry I am carrying about us. I want to tell you, because I would rather have it in the open than carry it on my own.' Many partners receive that better than the equivalent confrontation about a specific trip. If you want help finding the words, my piece on how to talk to your partner about sex has an approach that carries over to other hard subjects, and how to stop arguing with your partner covers what to do if the conversation tends to escalate.
If you already know something has happened
If you have discovered an affair, or your partner has told you about one, or you have known for a while and the summer has surfaced it again, this section is for you. The territory here is qualitatively different from worry and demands a different response.
What you might be feeling
The first days can feel like the floor has gone. In an interview study of 13 people who had completed a treatment trial for distress following romantic betrayal, the participants experienced the betrayal as shocking and destabilising, few had thought of their reaction as traumatic stress, and many found the intensity of what they felt hard to understand. When they met books and interviews that used a trauma framework to explain the effects of betrayal, they described clarity, validation and relief (Lonergan et al., 2021). It was a small study, but it fits what I hear. A lot of people simply assume something is wrong with them for not coping better than they are. Nothing is wrong with you. I have written about the first two weeks after finding out, and about why emotional affairs can hurt as much as physical ones.
Is it the end of the relationship?
Infidelity is one of the most difficult things a couple can move through together, but it is not automatically the end of the relationship. A small study followed 19 couples who had experienced an affair, within a larger trial of couple therapy. It found that couples who revealed the affair before or during therapy showed greater improvement in relationship satisfaction than couples who had not experienced infidelity (Atkins et al., 2005). That is a small, exploratory study, so it shows what is possible and not what is likely. A more recent pilot trial compared the Gottman Method with treatment as usual for couples dealing with infidelity. Forty nine couples were randomised and nineteen completed the assessments, so it is early stage evidence, and its authors include the Gottmans, who developed the method. They reported that the Gottman approach was more effective overall across trust, conflict management, relationship satisfaction, and the quality of the couple's sex (Irvine et al., 2024). There is no correct answer to whether a relationship should survive an affair. There is only what feels right to each partner, given the specifics. I cover this in more depth in healing from infidelity and rebuilding trust and in what healing looks like a year later.
There is rarely any need to decide quickly
There is rarely any need to decide whether to stay or separate in the first days or weeks. Decisions made in the immediate aftermath of discovery are often regretted by one or both partners later, in either direction. Holding the question open for longer than feels comfortable is usually wiser than resolving it quickly.
How therapy can help
Working with a couples therapist after infidelity can help. The work is not about deciding for you whether to stay. It is about helping both partners think clearly about what they want, what happened, and what would need to be true for the relationship to continue. If you are on your own, individual support is also worth considering, and a free consultation is a low pressure way to find out which fits.
When to consider couples therapy
The signals worth taking seriously, in roughly increasing order of urgency:
You have a low grade worry about your relationship that has attached itself to a specific summer event, and the worry is not going away when the event passes.
Something happened, or you suspect something happened, and you have not been able to talk about it with your partner directly.
You are doing things in response to worry that you would not normally do: checking their phone, tracking them, scrolling through their social media, lying awake imagining.
Your partner has disclosed an affair, or you have discovered one, and you are not sure what to do next.
You and your partner have been trying to recover from an affair for some months and are not making progress.
The broader piece on when to go to couples therapy covers the full range of signals worth paying attention to. If your partner is reluctant to consider therapy, there is a piece written for you, what to do when your partner won't go to couples therapy, and a companion piece for them, an honest guide for the sceptic.
A final thought
Most of what circulates online about summer infidelity is louder than it is accurate. A seasonal effect is plausible, and the reasons for it are mostly about travel, changed routines and removal from everyday accountability. The better evidence points to the people and the relationship, and it shows that holidays can be a moment when couples reassess. But summer does not transform people into other people. Couples in stable relationships generally remain in stable relationships through summer. Couples whose relationships are in real trouble may find that summer surfaces the trouble, but summer is rarely the cause.
If you have arrived at this article through quiet worry, the most useful thing is often to notice what the worry is really about, and to consider whether it points to a conversation with your partner rather than to a search engine. If you have arrived because something has already happened, the path forward is genuinely workable, even when it does not feel that way in the first weeks.
If you would like to talk about any of this in a low stakes way, an initial consultation might be a good idea. It is a conversation, not a session. You can book it on your own, or together if both of you are ready to think about something.
About the author
Mark Ryan is a BACP Accredited Psychotherapist and NCPS Accredited Relationship Therapist working with individuals and couples across three central London locations: Kensington, Pimlico, and Angel. His practice focuses on relationships, intimacy, and sexuality, with particular experience supporting LGBTQ+ couples and clients navigating non-traditional relationship structures.
If you would like to talk about whether couples or individual relational therapy might help, you can book a free thirty-minute consultation, available in person or online.
References
Atkins, D. C., Eldridge, K. A., Baucom, D. H., & Christensen, A. (2005). Infidelity and behavioral couple therapy: Optimism in the face of betrayal. Journal of Consulting and Clinical Psychology, 73(1), 144 to 150.
Blow, A. J., & Hartnett, K. (2005). Infidelity in committed relationships II: A substantive review. Journal of Marital and Family Therapy, 31(2), 217 to 233.
Brines, J., & Serafini, B. (2016). Seasonal variation in divorce filings: The importance of family ritual in a post sentimental era. [Conference paper]. American Sociological Association Annual Meeting. Retrieved 5 October 2026.
Irvine, T. J., Peluso, P. R., Benson, K., Cole, C., Cole, D., Gottman, J. M., & Schwartz Gottman, J. (2024). A pilot study examining the effectiveness of Gottman Method Couples Therapy over treatment as usual approaches for treating couples dealing with infidelity. The Family Journal, 32(1), 81 to 94.
Lonergan, M., Brunet, A., Rivest Beauregard, M., & Groleau, D. (2021). Is romantic partner betrayal a form of traumatic experience? A qualitative study. Stress and Health, 37(1), 19 to 31.
Mark, K. P., Janssen, E., & Milhausen, R. R. (2011). Infidelity in heterosexual couples: Demographic, interpersonal, and personality related predictors of extradyadic sex. Archives of Sexual Behavior, 40(5), 971 to 982.
Whisman, M. A., & Snyder, D. K. (2007). Sexual infidelity in a national survey of American women: Differences in prevalence and correlates as a function of method of assessment. Journal of Family Psychology, 21(2), 147 to 154.
