Some extreme cold events have occurred in the past few years. Human perceptual responses and cogni-tive performances when exposed to extremely cold environments could be significantly influenced. Impaired cognition can result in human errors and other cascading impacts. This paper aims to investi-gate human thermal perception and cognitive performance in an extremely cold environment in a cli-matic chamber. The study involved and exposed twelve male participants who wore protective clothing (2.16 clo) to a-20 degrees C climate chamber. Critical parameters for evaluating human perceptual response and cognitive performance, including thermal sensation vote (TSV), thermal comfort vote (TCV), mood, health symptoms, and selective attention performance, were recorded and analyzed. The results showed that the TSV did not recover to the value before the cold exposure despite the subjects being rewarmed in a neutral environment for 40 min. The participants' TSV reached the coldest after 20-25 min. Cold exposure increased discomfort, which required more than 40 min to recover. The extre-mely cold exposure resulted in increased tension, anger, confusion, decreased depression and fatigue. Anger and confusion had a strong correlation with tension-anxiety, and the correlation was stronger after recovery. The extremely cold exposure had a sustained impact on selective attention and heart rate. The reaction speed decreased by 36%. The results could be used to form recommendations to protect workers' health and performance when exposed to extremely cold environments. (c) 2021 Elsevier B.V. All rights reserved.