It’s 1992. Your mom just took you through the Dairy Queen drive in after supper. It was 30C today, and it’s going to be 35C tomorrow. You’re going to go swimming at the local outdoor pool with your mom, little brother, auntie and favourite cousin, tomorrow though. Mom will probably put on that Blue Rodeo tape on the way back. It’s not your favorite, but you find yourself waiting for the song hooks.
Life is simple and life is good.
My method:
Water freezes at 0°C (about 30°F) and boils at 100°C (about 210°F).
100°F is about half way between those two numbers on the Fahrenheit scale, but closer to the lower one.
On the Celsius scale I would describe 40°C the same way.
100°F ≈ 40°C