Quick answer
20°C is a boundary
Common reference
- 1.0–2.5 TOG boundary in common guidance
Under the bag
- Light fitted sleepwear; follow the product guide
Check
- Fit around neck and shoulders
- Neck or upper-back comfort later
Why this TOG range?
Common guidance places 2.5 TOG around 16–20°C and 1.0 TOG around 20–24°C. At exactly 20°C, use the temperature range printed for your specific sleeping bag and keep the clothing underneath light and adjustable.