Sleeping Hot: Everything You Need to Know

June 26, 2020 | Casper Editorial Team

There’s nothing quite like slipping into bed. Cool at first, we begin to warm up under the sheets and arrive at the perfect temperature just in time to fall asleep. But the sleep environment continues to heat up as the hours tick on. At some point, many of us start to get sweaty. Why? In fact, more than half of Americans experience sleeping “too hot” at least occasionally, as revealed by a recent Gallup and Casper Sleep Study. What causes this?

2 in 3 people say that temperature can cause sleep disruption and diminishing sleep quality. That’s why we made Snow Technology. New features like QuickCool™ Cover and HeatDelete™ Bands make it easy for you to keep your cool.

Why Do We Get So Hot When We Sleep?

The reason people “sleep hot” has a lot to do with design. Our core body temperature drops by a couple of degrees during the night, shedding heat into the surrounding areas, and certain sheets and mattresses trap the heat and moisture around us. This problem is especially acute for certain groups: for instance, according to our research, women are 50% more likely than men to struggle with controlling their temperature while sleeping, leading to an adverse impact on their quality of sleep.

This is especially true of memory foam mattresses and sheets with a high thread count (which are incredibly dense). We see the impact in tests we run in our California lab. Bedding design and your sleeping environment are the most common reasons people get so hot when they sleep.

What Causes Night Sweats?

Getting hot during sleep is normal and often has a quick fix. However, some people experience night sweats. Night sweats refer to when the body excessively sweats during the night. They are hot flashes that happen during sleep that are unrelated to the overheated environment you sleep in.
There are several different causes of night sweats including menopause, certain medications, cancers, infections, hormone disorders, neurological disorders, and more. We recommend visiting a doctor to uncover the real reason you may be experiencing night sweats.


Exploring the Science of Sleeping Hot


Hot sleeping, aside from being a comfort issue, can also result in less than ideal sleep durations. In fact, those who sleep too hot are 34% more likely to have slept fewer than six hours than those who were comfortable throughout the night, according to our sleep study with Gallup.

To dive deep into the science of sleeping hot, we had our senior mechanical engineer at Casper, Jordan Lay, do some research. He has outlined his main findings below.
As someone who naturally sleeps hot, I set up an experiment to better understand what’s happening under the covers. I designed custom ambient temperature and humidity sensors and wore them on my back and feet for several weeks. Then I pulled some generic bedding up around my shoulders and drifted off to sleep. What emerged through the data was a picture of a “hot sleeper.” Here’s a typical night of mine.
The temperature under the covers fluctuated significantly. What I found is that it skyrocketed soon after bedtime (climbing about 25 degrees) and then stayed within a certain band over the course of the night (hovering around 95 degrees). However, this wasn’t all that dramatic.
The relative humidity is where we see big swings. If you look at the relative humidity graph, from the same night, you can see that the moisture in the air jumped up and down. It climbed aggressively from midnight until about 3:00 a.m. and then plunged. What happened is that I woke up sweaty and had to flush the covers with fresh air, because the high humidity, paired with the elevated temperature, felt awful. The environment forced me to wake up.
If you experience similar heat fluctuations, you’re probably a hot sleeper. The body is usually good at keeping the body at the same temperature—it is our sleeping environment that causes us to sleep hot and drift away from a good night’s sleep.

How to Sleep When It’s Hot + Tips to Cool Down

Whether you’re naturally a hot sleeper or you struggle with poor sleep in hot weather, below are some of our top tips for how to cool down when you sleep hot:

  • Get a mattress with cooling properties: Cooling mattresses like the Casper Wave contain wool-infused covers and airflow perforations that help with temperature regulation. Opting for gel foam instead of memory foam can also help keep away the heat.
  • Set your thermostat to an ideal temperature between 60 and 67 degrees Fahrenheit: This is the best temperature for sleep. However, if you sleep hot, consider a thermostat setting of an even cooler temperature. In the end, the optimal temperature for sleeping is largely determined by your personal preference.
  • Wear breathable clothing: Wear lightweight, loose clothing to bed or consider sleeping naked to cool down for better sleep.
  • Take a hot shower or bath: Your body heat will rise in the shower or bath and when you get out it will begin to cool down, signaling to your body that it’s time for bed.
  • Sleep on breathable & cooling sheets: Airy linen sheets have moisture-wicking qualities designed to help you stay cool, even in summer months.
  • Use a fan or air conditioning: Fans or air conditioners can help lower your body temperature. If you have a ceiling fan, set it to run counter-clockwise — the airflow will create a wind-chill breeze effect to cool the room, lowering your bedroom temperature.
  • Kick out your furry friends: We all love to sleep with our dogs, but if you can’t fall into a deep sleep because you’re too hot, your furry friend could be the culprit.

Best Mattress for Hot Sleepers

Throughout our research, we’ve seen sleeping hot be a common problem for people. Even if the room is at the perfect sleep temperature of 60–67 degrees and doesn’t change, there are significant fluctuations in relative humidity under the covers; it’s often caused by dense bedding products that restrict proper airflow. We’ve incorporated a lot of these learnings into the products we design at Casper.
The body is good at keeping itself at the right temperature during sleep, so we create products that help support it in sleeping naturally. We designed the Casper sheets and pillow to promote balanced airflow by focusing on just the right thread count, weave, and fibers. We also engineered a custom layer for the Casper mattress that helps to balance heat and move it away from the body, improving sleep quality. Given that we spend about one-third of our lives in bed, it’s important to find a mattress and bedding that have cooling properties if you are someone who typically sleeps hot. Optimal sleep is just a few clicks away, with Casper.


  1. “Ceiling Fan Installation and Usage Tips.” n.d. ENERGY STAR.
  2. Inc, Gallup. 2023. “Sleep Temperature Linked to Overall Sleep Quality, Wellbeing.” June 21, 2023.