We propose that turning on the light can turn on the hot emotional system. Across six studies we show that ambient brightness makes people feel warmer, which increases the intensity of their affective response, including sensation seeking from spicy-hot foods, perception of aggression and sexiness ("hotness") in others, and generating more extreme affective reactions toward positive and negative words and drinks. We suggest that these effects arise because light underlies perception of heat, and perception of heat can trigger the hot emotional system. Thus, turning down the light, effortless and unassuming as it may seem, can reduce emotionality in everyday decisions, most of which take place under bright light. (C) 2014 Society for Consumer Psychology. Published by Elsevier Inc. All rights reserved.