A three-month survey of bedroom climate in the transition season from spring to summer in the Washington, D. C., area is presented. It showed nearly complete independence from outdoor conditions during the period when central heating was needed and windos were closed. Later in the season, with open windows, nocturnal temperature drop indoors averaged about 1.6° C, while humidity increased about 6%. As the season progressed evening conditions approached discomfort and exceeded the limit of sultriness several times. But with mechanical ventilation cooling powers and comfort numbers in the optimal zone could be re-established.