Geraniums prefer a temperature range of 60-75°F (15-24°C) during the day and 50-60°F (10-15°C) at night. They also prefer moderate to high humidity levels, around 50-60%. To adjust the temperature and humidity for a geranium, it is best to keep them in a room with a consistent temperature and humidity level. If the air is too dry, mist the plant regularly or place a tray of water near the plant to increase humidity. If the air is too hot, keep them in a shaded area or use a fan to circulate air. If the air is too cold, move them to a warmer area or use a heating pad to increase the temperature.