The point is pick a temperature and stick with it . Choose one which will be easy to maintain year-round. I find it's easier for me to heat my darkroom to 23 o C, allowing all my chemicals to reach equilibrium with that temperature. Then I don't have to worry about solutions cooling off or heating up during the course of my development process due to an ambient temperature difference. This fluctuation introduces a variable which will throw your results off.
Many people try to solve the temperature problem by using water baths and automatic processors.
But, in this discussion, I'm keeping the process simple and within easy reach of the average darkroom worker. Shoot another roll of film just like you did last time. Use the chart from Part One to plan your shoot. This means you'll have to move your lights either forward or backward to maintain the same camera settings. Don't forget, your meter setting has changed.