The combination of a swelling population, constant usage of electrical appliances, 24-hr eateries and vehicles have driven up ambient temperatures. Nights in Singapore are now noticeably warmer than it were decades ago. Night temperatures of above 30 degree celcius are now much more a common occurrence. The sweltering heat, when combined with high humidity can make life unbearable for those without air-conditioning. But assuming everyone turned on their AC's, the ambient temperature will rise further as all electrical appliances generate heat.