Feel Different When It’s Hot Out? How the Warmer Weather Impacts Your Hormones

It’s summertime and the warm sun is washing down on you. If you’re in the summer-loving camp, you might find that this feels really good. For others, the heat and humidity can actually mess with their moods and make them grumpier, despite the bright, sunny weather.

These reactions may all occur because of how summer (and its warmer temps) impact your hormones. Here, we answered some of your top questions about what happens to your hormones during the sweaty season.

One of the biggest changes in hormone levels as you step out into the warm sunshine: Vitamin D levels tend to rise. Though you might think of vitamin D as a nutrient, D is actually a hormone produced by the kidneys, notes the Endocrine Society. D helps regulate your immune system to fend off illness, support mental health, and play an important role in building bone to keep your skeleton strong.

Your skin produces vitamin D in response to UV light, and research shows that vitamin D levels rise during the spring and summer thanks to warmer temps that get us outside more and increase sun exposure. As a result, more people have sufficient levels of D in the summer compared to winter.

What’s more, people in the study who exercise at least once a week also have higher vitamin D levels, likely because that exercise was done outside, say researchers.

It’s not the weather per se that’s causing hormones to go haywire. Rather, there’s a natural seasonal variation in some hormone levels that happens throughout the year.

One: Cortisol. Levels of cortisol---the stress hormone---in your saliva are generally higher in the summer compared to the winter, finds a small 2019 study in the Journal of Applied Physiology. While cortisol is dubbed as the stress hormone, and we’re generally warned that cortisol is bad, it is a necessary, “life-sustaining” hormone that keeps your body in balance, the researchers say.

It’s not exactly clear why this boost in cortisol occurs. It may be due to more light exposure from longer days and shorter nights, as well as hotter temperatures that increase stress.

There’s a wider body of research that suggests that outside temps play a larger role in your mood---and it might surprise you. A 2021 systematic review and meta-analysis on 53 studies published in Environment International concluded that as temperatures rise, the risk of mood, mental health, and anxiety disorders also increase, with greater odds during heatwaves that persist for at least three days.

Hot weather has been found to affect levels of neurotransmitters in the brain that impact mood and cognitive function, say researchers. Heat waves, in particular, trigger irritability, distress, aggression, and violence. Elevated temps may also provoke inflammation in the brain, as well as sleep problems that underlie depression.

There’s some research that being deficient in vitamin D was associated with three times the odds of having a long menstrual cycle (defined as one that’s more than 35 days). Why? It looks like having lower vitamin D is linked to a delay in ovulation. On the flipside, higher D levels---which often occur in the summer with increased sunshine---may be able to help regulate your cycle.

Other research, however, has not found that the menstrual cycle changes across seasons.

If you wait for summer all year long only to feel physically or mentally blah, you’re going to want to figure out what’s going on.

First, get your vitamin D level checked. If you are supplementing, you may only need to do so during the fall and winter months, and may be able to stop in the summer. Check with your doctor. You can get testing in-office or with Base’s Energy Testing Plan. Specifically, the Focus Test is an at-home test that looks at vitamin D levels to see if yours may be linked to your ability to stay energized and cognitively on your game throughout the day.

Since vitamin D levels were highest in outdoor exercisers, consider that a reason to move your workouts outdoors when the weather is nice.

While more research needs to be done on the connection between summer, hot weather, and cortisol, having higher cortisol levels in the summer only underscores the importance of making healthy lifestyle choices now at this time to effectively manage stress. That includes eating a plant-packed diet (summer is the perfect time to go after all the delicious looking fruits and veggies), exercising regularly, and practicing stress management strategies, whether that’s mindfulness, setting boundaries in your work and personal life, or spending more time with friends and loved ones.

Your cortisol levels are a marker of how well your body is handling stress. You can explore cortisol testing through your doctor. Or, if you’d like an at-home option, Base’s Stress Testing Plan, particularly the Cortisol Test, can analyze morning, evening, and nighttime cortisol levels to give you a clear picture of how your body is reacting throughout the day.

Lastly, if you are a person who has a period who’s struggling with irregular menstrual cycles, terrible PMS symptoms, or are concerned about your fertility, share your concerns with your gynecologist or ob-gyn, who can suggest therapies, from hormonal birth control to over-the-counter medication and lifestyle changes that can help improve your cycle.  

Being aware of what’s going on with your body, looking inward to investigate your hormone levels if needed, and making adjustments to your daily routine, can improve your health and wellbeing—and help you thrive during the summer, no matter how hot it gets.