Our interest in sex doesn’t stay the same throughout the year—it changes with the seasons. And right now, we’re at peak sex.

Numerous scientific studies have found that there’s a reliable increase in sexual interest and activity during the early summer months (a second peak occurs in December, but that’s a story for another, colder day). Let’s take a look at the evidence.

Our browser histories tell a big part of the story. An analysis of Google search trends published in the Archives of Sexual Behavior revealed that searches related to pornography (think search terms like boobs, sex and MILF), prostitution (escort, massage parlor, and brothel) and online dating (from Match.com to OkCupid) are all consistently higher in the summer compared to the spring and fall. This isn’t simply because people do more googling in the summer—searches for pets, car parts and popular websites including Facebook don’t follow a reliable cycle throughout the year. Instead, this seasonal search trend is therefore specific to sex.

Increase in sexual interest isn’t just playing out on our computers and smartphones. We can see it in our actual sexual behaviors, too. For example, studies have found that, in the summer, people report having more sex, condom sales go through the roof and teenagers are more likely to report losing their virginity. Not only that, but STD clinics find that patients who visit in the summer report having the highest number of recent sex partners. Perhaps not surprisingly, these clinics diagnose more STDs in the summer, too.

In the summer, we subconsciously transfer the excitement of our outdoor activities to our bedrooms.

The logical question you’re probably asking yourself right now is why? What’s behind this peak in summer sex? What we’re seeing here is a biopsychosocial phenomenon, meaning there are biological, psychological and social/environmental factors that are conspiring to change our sexual behavior pattern.

Let’s start with biology. In the summer, the days are longer and we’re exposed to more sunlight, which increases the body’s production of the neurotransmitter serotonin. Serotonin is a brain chemical that makes us feel good—and that’s why the most popular anti-depressant drugs are designed to boost it.

Research has found that serotonin levels are generally higher in the summer than they are in the winter, which helps to explain why we see corresponding mood changes throughout the year, including higher levels of depression in the winter. So what does this mean for our sex lives? Well, if people are happier in the summer due to changes in brain chemistry, they’ll probably be more inclined to engage in activities that have the potential to lead to sex, like going out to bars and clubs or going on dates. By contrast, if you have the winter blues, you’re probably less likely to venture out of the house and socialize, thereby creating fewer opportunities for sex. Also, if you’re already in a positive mood state, it’s just easier to feel other positive moods, like the one we experience when we’re sexually aroused.

There’s a lot more to this story than serotonin, though—and this is where psychology comes into play. In the summer months, we tend to do more exciting and novel things. For example, you might go on vacation, visit a theme park like Universal Studios or Six Flags or join a recreational sports league. All of this excitement has the effect of amping up our physiological arousal, which, it turns out, often gets transformed into sexual arousal.

This is something psychologists call excitation transfer theory, and it basically means that excitement from one stimulus has the potential to intensify our excitement to another. For example, in a 2003 study, researchers approached people at an amusement park who had either just gotten off of a roller coaster or who were waiting in line to ride one. Participants were then asked to rate the attractiveness and desirability of a photo of someone of the opposite sex. The researchers reported that single people who had just exited the ride rated the target as more attractive than people who were waiting in line.

What this tells us is that part of the increase we’re seeing in summer sex might just be that we’re subconsciously transferring the excitement of our outdoor activities to our bedrooms.

On top of this, several social and environmental factors play a role, too. One is that summer offers a more sexualized environment than other seasons. As psychologist Dr. Nicole Prause described in an email, “It’s hard to find sexual cues when everyone is bundled head to toe, then hard to stop seeing them with whatever is happening with shorts these days.” So, it’s no wonder we have sex on the brain in the summer—we’re just bombarded with cues and reminders of sex everywhere we go.

And then there’s the fact that many of us have more free time in the summer. Teens are on summer break, and all of that time off coupled with less adult supervision helps to explain the aforementioned spike in summer virginity loss. As for adults, summer vacations offer relief from stress. Stress can put a big damper on sexual desire, so any opportunity to get away from it—even if it’s temporary—is going to make it easier to get in the mood for sex.

So, if you’ve found that you’re hornier than usual lately, you’re not alone. In the summer, our bodies, activities and environments change in dramatic ways that set the stage for feeling sexually liberated. To which we say, let freedom ring.


Justin Lehmiller, PhD is a sex educator and researcher at Ball State University, a Faculty Affiliate of The Kinsey Institute, and author of the blog Sex and Psychology. Follow him on Twitter @JustinLehmiller.