Sudden or extreme temperature changes can have various effects on the body, and whether they are "bad" depends on the individual and the specific circumstances. Here are some considerations:

Heat Exposure:

Heat Stress: Exposure to high temperatures can lead to heat stress or heat-related illnesses, such as heat exhaustion or heatstroke. It's essential to stay hydrated, take breaks in the shade, and avoid prolonged exposure to extreme heat.
Cold Exposure:

Hypothermia: Exposure to extremely cold temperatures can lead to hypothermia, a potentially life-threatening condition where the body loses heat faster than it can produce it. Proper clothing and shelter are crucial in cold environments.
Adaptation:

Acclimatization: The body can adapt to changes in temperature over time. For example, through acclimatization, individuals may become more tolerant of heat or cold.
Individual Variability:

Individual Differences: People vary in their sensitivity to temperature changes. What might be uncomfortable for one person may be tolerable for another.