comfort zone

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The range of temperature, humidity and ventilation that a building's occupants feel to be comfortable
• noun by extension The range of circumstances in which a person feels relaxed or able to cope

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the temperature range (between 28 and 30 degrees Centigrade) at which the naked human body is able to maintain a heat balance without shivering or sweating