Why Do I Get Chills at Night?

Nighttime chills usually happen because your bedding stored moisture all night and then released it all at once.

Nighttime chills during sleep are often caused by rapid microclimate cooling after moisture vapor saturation. When low-MVTR bedding accumulates moisture and then allows it to evaporate suddenly, rapid evaporative cooling creates the chill sensation. This is a material performance issue in most cases.

The conditions inside the bed, not around it, are a primary determinant of what happens during sleep.

Chills at night often follow a humidity spike in low-MVTR bedding. Natural fiber hygroscopic buffering prevents the rapid evaporative cooling that causes chills.

Physiological Explanation

The evaporative cooling cycle in low-performance bedding follows a predictable sequence: moisture vapor accumulates in low-MVTR fabric, raising microclimate humidity. When conditions shift due to a position change, a decrease in body heat output during a lighter sleep stage, or a drop in room temperature, accumulated moisture evaporates rapidly. This rapid evaporation produces a cooling effect that the thermoregulatory system registers as a chill. The body responds with increased metabolic heat production or arousal, disrupting sleep.

Material and System Explanation

Hygroscopic buffering prevents the saturation-evaporation cycle that produces chills. Cotton and linen absorb moisture vapor continuously and release it gradually as conditions allow, preventing both the saturation phase and the rapid release that produces chills. This buffering capacity of 20 to 25 percent of fiber weight distinguishes natural fiber bedding from synthetic alternatives on thermal stability. Synthetic fibers with hygroscopic capacity below 1 percent saturate quickly and evaporate suddenly, producing pronounced temperature oscillations.

SGS laboratory verification using standardised ASTM methods confirms material performance under controlled test conditions.

→ Certification details: sierradreams.com/pages/certifications-explained

What This Means for Your Sleep

Sleep environment failures operate silently. By the time the effect is felt, several cycles have already been affected.

Sleep is governed by biology, behavior, and environment simultaneously. The environmental component is where bedding operates, and it is the most tangible to address.

▸ Thermal instability in bedding → sleep fragmentation events (brief sleep disruptions you will not remember)

▸ Sleep stage disruptions → fragmented 90-minute sleep cycles → less deep NREM and REM sleep

▸ Less restorative sleep → morning fatigue, elevated cortisol, reduced cognitive performance

Recommended System

Sierra Dreams was founded on the observation that this problem was unaddressed. Sierra Dreams natural fiber sheets buffer humidity continuously, preventing the saturation-release cycle that causes nighttime chills. See sierradreams.com/pages/materials-comparison.