Your body needs to lower its core temperature by about 1–2°C to initiate and maintain deep sleep. This is why cool rooms dramatically improve sleep quality — they help accelerate that drop.

The scientific consensus points to 15–19°C (59–66°F) as the optimal bedroom range, with 16°C being the most commonly cited ideal. Above 20°C, the body struggles to shed heat efficiently, reducing slow-wave and REM sleep.

This forecast estimates your indoor temperature by combining the outdoor night temperature with a heat retention factor: the hotter your day was, the more warmth your home will hold into the night.

Humidity affects how well your body can cool itself through perspiration. Too low (under 40%) and your airways dry out, leading to snoring, congestion, and restless sleep. Too high (above 60%) and it becomes difficult for sweat to evaporate, making you feel hot and clammy.

The 40–55% range keeps airways comfortable and allows effective thermoregulation throughout the night.

PM2.5 refers to fine particulate matter — tiny particles 2.5 micrometres or smaller. These are small enough to penetrate deep into lung tissue. During sleep, breathing becomes slower and more regular, but you're spending 7–9 hours continuously breathing whatever is in your room.

Studies link elevated PM2.5 levels to reduced sleep efficiency, more nighttime awakenings, and shorter overall sleep duration. Even moderate levels over time are associated with disrupted sleep architecture.

Ground-level ozone (O₃) is a reactive gas that forms when sunlight reacts with vehicle and industrial emissions. Unlike the protective ozone layer high in the atmosphere, ground-level ozone is an irritant that affects the respiratory system.

Elevated ozone can cause airway inflammation and mild breathing difficulty, which disrupts sleep — particularly for those with asthma or allergies. Levels typically peak in the afternoon and drop overnight, but hot, stagnant days can keep them elevated into the evening.

The idea that the full moon disrupts sleep has been dismissed as folklore for centuries — but the evidence is more nuanced. A well-cited 2013 study in Current Biology found that around the full moon, participants took 5 minutes longer to fall asleep, slept 20 minutes less overall, and showed reduced deep-sleep brain activity — even in a windowless lab with no moonlight exposure.

The leading hypothesis involves circadian rhythm entrainment: human biology may have evolved a subtle internal lunar rhythm. A secondary mechanism is simply light exposure — a bright full moon rising early can suppress melatonin, especially through uncovered windows.