A suitable temperature for a child's sleeping climate is 16-24°C (61-75°F). Factors that may affect the temperature in the sleep bag are climate, room/body temperature and amount of garments. Below is just a guide for how to dress a child at various room temperatures with a sleep bag that has a TOG value of 1:
At 22-24°C (71-75°F) – short-sleeved onesie.
At 20-22°C (69-71°F) – long-sleeved onesie.
At 18-20°C (64-69°F) – pyjamas.
At 16-18°C (61-64°F) – long-sleeved onesie+pyjamas.