When it comes to your period, you’ve probably learned by now that you should never get too comfortable with your cycle. Most of us will experience changes in the length of our cycle, fluctuations in flow and even changing PMS symptoms. And there’s another possibility — perhaps your menstrual cycle changes with seasons, too.

If so, you’re not imagining it. It’s a recorded phenomenon, and here’s how the shifts from winter to spring to summer to fall might be affecting you!

1. Warm Weather Fights Moodiness

When it comes to mood swings in women, PMS is one of the four leading causes. Hormonal changes, stress and menopause can also cause our feelings to ebb and flow at an unpredictable pace.

In the lead-up to your period, then, you might be feeling moodier than usual. One of the ways your menstrual cycle changes with seasons is that sunny springs and summers scientifically make us feel happier, thus warding off the wrath of a typically moody PMS cycle.

Here’s how it works — when the sun’s out and our bodies have the chance to soak up its rays, our bodies respond positively. They begin to churn out more vitamin D and dopamine. A lack of vitamin D has known links to depression, and many Americans do not get enough of it because they spend so much time indoors. When it’s spring or summer, though, the sun creeps back out and entices us to head outside. A morning walk or an afternoon by the pool can instantly make us feel good because we got a rush of vitamin D. Similarly, a healthy level of dopamine fights off both depression and mania.

To that end, warm weather inspires us to go outside and get moving, which can also relieve some of the pains and aches that come with our periods. So with a combination of sunshine, vitamin D, dopamine and a bit of sweat, spring and summer bring about the first of the ways your menstrual cycle changes with seasons.

Your menstrual cycle may shorten during the summer months as well. A recent study revealed that women release more follicle stimulating hormone (FSH) during sunnier times of year, the summer months in the northern hemisphere. This resulted in a decrease in cycle length by nearly one full day. Due to increased ovulation from increases in this hormone, women may find conceiving easier during the summer months if they’ve been trying to get pregnant.

Does this mean all seasonal menstrual changes during the summer are positive? Not exactly. If you’re prone to yeast infections, you may find you suffer more during the warmer months. These can lead to irregular menstrual cycles in some women.

Researchers believe women suffer more infections during the summer less due to the weather and more due to increased activity levels. Women who wear their sweaty leggings from gym to store or who walk around in damp bathing suits create the perfect breeding ground for fungi and bacteria. When swimming, change out of your wet suit soon after leaving the water, and opt for loose-fitting, breathable clothing whenever possible.

Additionally, if you’re prone to yeast infections, try increasing your consumption of probiotics. While foods like yogurt foster healthy intestinal bacteria, they also help to balance your vagina flora. If you enjoy sipping your probiotics, opt for kefir or kombucha — both are vegan-friendly if you follow a cruelty-free lifestyle.

During the summer, the periodic bloating which occurs due to changes in menstrual cycles prove particularly troublesome for many women. You don’t want to turn down a day at the beach because your belly makes you feel like Moby Dick in your bikini! If you do experience premenstrual bloating, try these tips to beat it quickly:

• Sip lemon water. Lemon acts as a natural diuretic, removing excess salt from the body. This tip works particularly well if your bloating results from caving to that craving for salty crisps the night before. And drinking more water, ironically enough, helps beat bloating, to.
• Try turmeric. Turmeric is a powerful anti-inflammatory. It also helps to ease menstrual cramps and relieve gas.
• Eat dark, leafy greens. Many greens like kale and spinach act as natural diuretics. They’re also chock-full of nutrients. Nosh on a spinach and Swiss chard salad with some avocado-based green goddess dressing for heart-healthy omega-3’s and belly-shrinking deliciousness.

To that end, warm weather inspires us to go outside and get moving, which can also relieve some of the pains and aches that come with our periods. So with a combination of sunshine, vitamin D, dopamine and a bit of sweat, spring and summer bring about the first of the ways your menstrual cycle changes with seasons.

2. Winter Weight Gain Contributes

It’s normal to put on a few pounds over the winter — in fact, there’s a scientific explanation as to why our bodies cling to calories when it’s cold. Long before humankind had cozy houses and central heating, our ancestors would spend winter trying to survive the frigid temperatures. As such, their bodies adjusted to hanging onto fat when it got cold — being overweight posed much less of a threat to their well-being than an underweight frame.

Nowadays, most people don’t have to worry about surviving in such a way, but our bodies still tend to hold onto extra pounds through the winter thanks to evolutionary instincts. Most of us will eventually work them off, whether on purpose or by instinctively eating less as the sun returns. But until then, winter weight gain can affect your period.

Here’s another clue to look out for if you think your menstrual cycle changes with seasons: Your flow could last longer or get heavier when you gain a few pounds over the winter. Of course, there’s no single formula for all women, and both under- and overweight women experience changes in their flow. For instance, a woman with a high BMI might experience amenorrhea, which means she doesn’t have a period, or she might have menorrhagia — a very heavy flow.

Your best bet to combat this side effect is to maintain your health regardless of the seasons. Read up on the best women’s health blogs, sign up for a fitness class, whip up nutritious winter stews — whatever gets you through as the healthiest version of yourself will help you avoid this seasonal shift in your period.

Be aware you cycle may last longer in winter. Just as it shortens with exposure to higher light levels, winter’s short days could increase your flow. Keep an extra pack of your favorite feminine hygiene products on hand, and treat yourself to some extra TLC in the form of a warm bath or even a leisurely day of binge-watching Netflix.

3. You May Be More Aware in Winter

In spring and summer, we’re likely to be busy — from beach vacations to weekend barbecues to summer sports leagues, we have plenty to keep us occupied. Plus, in summer, we can wear lightweight, flowy clothes and get more exercise from merely spending time in the sun, as we’ve already mentioned. This bliss comes with a bonus — we might perceive our periods to be less painful during the summer months.

Think about it this way — in the winter, we pack ourselves into layers and commute to work in freezing weather. Many struggle with seasonal affective disorder in the winter as well. Adding intense period cramps, hormonal acne or an irritable mood swing on top of that makes matters worse. In other words, your pre- or post-menstrual syndrome is still alive and well. Your period flows the same and lasts just as long as it does in summer, but the weather sometimes makes it seem worse.

The combination of SAD with menstrual changes can trigger major depressive disorder in some women. It’s normal to feel more tired when days grow shorter, but extreme fatigue when combined with other symptoms gives cause for alarm. Seek medical attention if you experience persistent feelings of sadness or hopelessness, changes in appetite, loss of interest in previously-enjoyable activities or thoughts of harming yourself.

Even if your worst depressive symptoms occur only prior to menstruation they still can disrupt your life significantly. Few employers look kindly upon staff who call out predictably the third Friday of every month, for example. Depression is treated through a combination of medication and talk therapy. Reach out to your employee assistance team if you have one, or contact your health insurer to find a list of network therapists.

How to Deal with Menstrual Cycle Changes with Seasons

One of the best ways to deal with your menstrual cycle changing with the seasons? Maintain perspective. Remember the things that make you happy, whether it’s hot or cold, sunny or snowy. Doing so, along with exercise and time spent outdoors, however short, will help keep you balanced throughout the year.