Newstalk Hard shoulder with Síne Dunne - Why it can be hard to sleep in the hot weather

Struggling to sleep in Ireland’s hot weather? You’re not alone. I joined Kieran Cuddihy on The Hard Shoulder on Newstalk this week to talk about exactly that. When summer temperatures rise, so do sleep problems — from trouble nodding off to frequent wake-ups and feeling groggy in the morning. In this expert guide, I break down how to sleep when it’s hot, why temperature matters for sleep quality, and what actually works to stay cool at night in Irish homes.

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Summer sleep struggles are real, and as temperatures rise, so do complaints about restless nights. Most people don't realise how much hot weather affects their sleep until they find themselves tossing and turning, waking repeatedly, or feeling groggy despite spending what felt like a full night in bed.

Why heat affects sleep

The discomfort is not just in your head. There's a physiological reason it becomes harder to sleep in the heat. Your body needs to cool down by one to two degrees to successfully transition into sleep. This natural drop in core temperature is part of your circadian rhythm—the internal system that governs your sleep and wake cycles. When your bedroom is too warm, that cooling process is delayed. You take longer to fall asleep, and you're more likely to wake during the night, especially during REM sleep, which is already a lighter, more temperature-sensitive stage.

When that drop in body temperature doesn't happen efficiently, your sleep architecture suffers. You may get less deep sleep and less REM sleep, which are essential for memory consolidation, emotional regulation, and physical repair. So even if you technically get eight hours in bed, it won't feel restorative.

The science of sleep and temperature

Temperature affects not just comfort, but the structure of your sleep. Studies show that once room temperature rises above 22 degrees Celsius, sleep quality begins to decline. At temperatures over 25 degrees, disruptions are significant, especially for children, women experiencing hormonal changes such as perimenopause, and older adults who already struggle to regulate body temperature effectively.

How to cool your room

There are a few core strategies that can significantly improve sleep quality during hot weather. First, manage the heat in your environment. Keeping blinds or blackout curtains closed during the day can prevent your room from turning into a greenhouse. In the evening, open windows to create a cross-breeze and let trapped heat escape. Use a fan to keep air circulating. For a stronger cooling effect, place a bowl of ice or a frozen water bottle in front of the fan to cool the airflow.

One surprisingly effective trick is freezing a hot water bottle. Fill it halfway, freeze it, then wrap it in a light towel and place it near your feet in bed. The feet are sensitive thermoregulators, and cooling them can help lower your core temperature more quickly. Alternatively, hug the frozen bottle to help bring down body temperature gradually.

The right shower temperature

Showering before bed is also helpful, but it’s important to avoid extremes. An icy cold shower can actually activate your stress response, making it harder to sleep. A lukewarm shower around 60 to 90 minutes before bed is ideal—it warms the skin slightly, prompting your body to cool itself naturally in the following hour, which aligns perfectly with your sleep timing.

Choose breathable bedding

Your choice of bedding and sleepwear makes a significant difference in how your body handles heat. Natural fabrics like cotton, bamboo, or linen are breathable and moisture-wicking. These materials help draw sweat away from the body and allow for airflow across the skin, supporting thermoregulation throughout the night. Polyester and other synthetic blends tend to trap heat and moisture, leading to a hot, clammy feeling.

One Irish brand doing this particularly well is Amurelle Sleepwear, which creates beautiful, breathable pieces using natural materials. Their sleepwear is not just stylish—it’s built for performance. Soft, lightweight and designed to promote airflow, Amurelle’s pieces help your body do what it’s naturally trying to do: cool down and stay cool.

At Siest Sleep, we designed our signature Sleepers for the same reason. They are lightweight, breathable and perfect for warm nights. Customers often find that switching to a Sleeper instead of using a duvet helps them fall asleep faster and wake up less. The materials used in our Sleepers are specifically chosen to prevent heat build-up, which is especially useful during Irish heatwaves, when traditional bedding becomes suffocating.

What to wear—or not wear—to bed

Another common question is whether it’s better to sleep naked or wear pyjamas when it’s hot. While going without clothing might seem cooler, breathable fabrics can actually help keep you more comfortable. Loose-fitting cotton or bamboo sleepwear absorbs sweat and allows for air circulation. Wearing nothing can sometimes lead to sweat pooling on the skin, which then evaporates less efficiently and can feel sticky.

Food, drink and timing

Your sleep habits and evening routine also play a role. Eating large or spicy meals late at night can increase your core temperature, making it harder to cool down. Caffeine and alcohol both impair thermoregulation and disrupt your sleep cycle, particularly in warm conditions. Try to finish eating at least two hours before bed and stay hydrated throughout the day—but avoid drinking too much right before bed to reduce the chance of middle-of-the-night wakeups.

Sharing a bed in the heat

If you share a bed, the challenge of staying cool doubles. Two warm bodies can quickly overheat a small space. One solution is using separate duvets, which allows for personal temperature control. You might also consider sleeping slightly apart to allow for better airflow. Some couples find that using a fan directed at the bed or investing in a cooling mattress topper makes a noticeable difference.

Best sleep positions for cooling

Sleeping position can also affect how hot you feel. The starfish position—lying on your back with arms and legs spread—maximises surface area and promotes cooling. Avoid curling up tightly, which conserves heat and reduces airflow around the body.

What we can learn from other countries

Many cultures have clever adaptations for sleeping in hot weather. In Japan, for instance, people sleep on lightweight tatami mats and use seasonal bedding, switching to ultra-thin covers in summer. Mediterranean countries often close shutters during the day to block heat and embrace midday rest periods—siestas—as a natural response to high temperatures. These habits aren’t just cultural; they’re smart biological adaptations.

Your sleep tracker will show it

If you wear a sleep tracker, you may notice patterns in your data during warmer months. It’s common to see increased sleep latency (the time it takes to fall asleep), more frequent wake-ups, and reduced deep and REM sleep. Your heart rate may also stay slightly elevated overnight, a sign that your body is working harder to regulate temperature.

It’s important not to panic about this data. The body is adaptable. But when you notice consistent disruptions, it’s a signal to take proactive steps to support your sleep. Environmental adjustments, light sleepwear, better hydration, and targeted evening habits all help.

Design your sleep for summer

To optimise your summer sleep, treat it like you would a summer meal. You don’t cook a heavy roast on a 28-degree evening. You prepare something lighter, simpler, and fresher. Your sleep deserves the same consideration. Cool the room, choose breathable materials, avoid overloading your system late at night, and create space—physically and mentally—for your body to unwind.

Good sleep in summer is not about luck. It’s about design. With a few adjustments, you can sleep well even on the warmest nights and wake up feeling clear-headed and ready to enjoy the long days ahead.

Disclaimer: This content is for informational purposes only and is not intended as medical advice. If you have ongoing sleep issues or health concerns, please consult a qualified healthcare professional.