If you've ever tossed and turned on a hot summer night, you already know how profoundly temperature affects sleep. What you might not realise is that temperature regulation isn't just about comfort—it's fundamentally intertwined with your body's ability to initiate and maintain sleep. Understanding the science behind thermoregulation can help you create conditions for consistently better rest, regardless of the season.
How Body Temperature Controls Sleep
Your core body temperature follows a predictable 24-hour cycle, rising during the day to promote alertness and dropping at night to facilitate sleep. This temperature rhythm is controlled by your circadian clock and closely linked to your sleep-wake cycle. The decline in core temperature—typically around 1-2°C—is actually a trigger for sleep onset, not just a consequence of it.
As evening approaches, your body begins shedding heat through a process called vasodilation, where blood vessels near the skin surface expand to release warmth. This is why your hands and feet often feel warm before you fall asleep—heat is being transferred from your core to your extremities and then radiated away.
When this cooling process is impaired—by a hot bedroom, heavy blankets, or a mattress that traps heat—falling asleep becomes more difficult, and sleep quality suffers throughout the night.
Research shows that the rate of temperature decline may be as important as the absolute temperature. A rapid drop in core temperature signals to your brain that it's time to sleep. This is why a warm bath before bed can paradoxically help you feel sleepy—the subsequent cooling when you get out accelerates the natural temperature drop.
The Ideal Sleeping Temperature
Sleep scientists generally agree that the optimal bedroom temperature for most adults falls between 15°C and 19°C (60-67°F). This range supports the natural cooling process and allows your body to maintain the lower temperature needed for quality sleep throughout the night.
This temperature might feel surprisingly cool when you first get into bed, but that's actually ideal. Your blankets should provide just enough insulation to feel comfortable without causing you to overheat as the night progresses.
Individual Variations
While the 15-19°C range works for most people, individual preferences vary based on several factors:
- Age: Older adults often prefer slightly warmer temperatures
- Body composition: People with higher body fat may tolerate cooler temperatures
- Metabolic rate: Those with faster metabolisms generate more body heat
- Hormonal factors: Menopause and menstrual cycles affect temperature regulation
- Health conditions: Some medical conditions affect thermoregulation
The best approach is to start within the recommended range and adjust based on how you feel. If you're consistently waking up sweating or shivering, adjust accordingly.
Why Heat Disrupts Sleep
Sleeping in an environment that's too warm creates multiple problems for sleep quality:
Difficulty Falling Asleep
When your body can't cool down efficiently, the natural sleep-onset signal doesn't work properly. You may lie awake feeling alert despite being tired, as your body struggles to achieve the temperature drop needed to trigger sleep.
Fragmented Sleep
Throughout the night, your body temperature continues to fluctuate within sleep cycles. An overly warm environment makes it harder to reach and maintain the deeper sleep stages, leading to more frequent awakenings and lighter, less restorative sleep.
Reduced REM Sleep
REM sleep is particularly sensitive to temperature. During REM, your body temporarily loses the ability to regulate temperature through shivering or sweating. If the environment is too hot, your brain may cut REM periods short to prevent overheating, reducing the total amount of this important sleep stage.
Your body temperature reaches its lowest point around 4-5am, coinciding with the peak of deep sleep. Maintaining a cool bedroom environment supports this natural pattern and maximises the amount of restorative deep sleep you achieve.
Cooling Strategies for Australian Sleepers
Australia's climate presents unique challenges for maintaining optimal sleep temperatures. Summer heatwaves can push bedroom temperatures well above comfortable levels, making good sleep difficult to achieve. Here are effective strategies for staying cool:
Bedroom Environment
- Air conditioning: If available, set your unit to 18-20°C for sleeping; use a timer to avoid running it all night
- Fans: Ceiling fans or pedestal fans improve air circulation; position them to create cross-ventilation
- Block daytime heat: Keep blinds and curtains closed during hot days to prevent heat buildup
- Ventilate at night: Open windows once outdoor temperatures drop below indoor temperatures
- Consider room placement: Sleep in the coolest room of your home during extreme heat
Bedding Choices
- Breathable sheets: Cotton, linen, or bamboo sheets wick moisture and allow airflow
- Lightweight blankets: Opt for thin cotton or bamboo blankets rather than doonas
- Cooling mattress toppers: Gel-infused or phase-change material toppers help dissipate heat
- Moisture-wicking pillowcases: Help keep your head and face cool throughout the night
Personal Cooling Techniques
- Pre-bed shower: A lukewarm shower before bed helps lower core temperature
- Cold water bottle: Keep a water bottle in the freezer and bring it to bed
- Damp towel: A cool, damp towel on your forehead or neck can help you fall asleep
- Loose sleepwear: Wear minimal, loose-fitting, breathable fabrics or sleep nude
- Hydration: Stay well-hydrated during the day, but limit fluids close to bedtime
On extremely hot nights, place your sheets in a plastic bag and put them in the freezer for 30 minutes before bed. They won't stay cold all night, but the initial cooling can help you fall asleep faster.
How Your Mattress Affects Temperature
Your mattress plays a significant role in temperature regulation during sleep. Different mattress materials have varying levels of breathability and heat retention:
- Traditional memory foam: Tends to trap body heat; newer formulations with gel or copper infusions improve cooling
- Latex: Naturally more breathable than memory foam; provides better airflow
- Innerspring: Coil systems allow air circulation; typically sleep cooler than all-foam options
- Hybrid: Combines foam comfort layers with coil support; offers moderate temperature regulation
If you consistently sleep hot, prioritise mattresses marketed as "cooling" or look for features like gel-infused foams, copper or graphite infusions, breathable covers, and coil systems that promote airflow.
Cold Sleepers: The Other Side
While most temperature-related sleep problems involve excess heat, some people struggle to stay warm enough during sleep. Cold extremities, in particular, can interfere with the vasodilation process needed for sleep onset.
If you tend to sleep cold:
- Wear socks to bed—warming feet promotes vasodilation and can hasten sleep onset
- Use a heated mattress pad or electric blanket (with safety precautions)
- Layer blankets for adjustable warmth
- Consider a heavier, more insulating mattress
- Drink warm (non-caffeinated) beverages before bed
Temperature and Sleep Partners
Sharing a bed with a partner who has different temperature preferences can be challenging. Body heat radiates between sleepers, and couples may have conflicting needs for covers and room temperature.
Solutions for couples with different temperature needs:
- Use separate blankets so each person can choose appropriate insulation
- Consider a mattress with dual-zone temperature control
- The cooler-sleeping partner can sleep closer to the air conditioning
- Invest in moisture-wicking sheets that work for both preferences
- Compromise on room temperature and adjust individual bedding
Creating Your Ideal Sleep Climate
Temperature regulation is a fundamental but often overlooked aspect of sleep hygiene. By understanding how thermoregulation affects your sleep and implementing appropriate cooling or warming strategies, you can significantly improve both how quickly you fall asleep and the quality of rest you achieve.
Start by setting your bedroom temperature to 16-18°C, choose breathable bedding materials, and pay attention to how temperature affects your sleep. Small adjustments can yield significant improvements in sleep quality, especially during Australia's challenging summer months.