Simplify the following text for a Grade 11 native English-speaking person.
Original: Warming centers are generally opened for only a few days at a time based on the conditions of the area , although some are open for specific portion of the year when weather conditions are adverse .
Simplified: Warming centers are generally opened for only a few days at a time based on the conditions of the area , although some are open for specific portion of the year when weather conditions are bad .