@dragonarchitect interesting. I've been doing surprisingly ok in California with only knowing this incomplete and approximate table:
32°F = 0°C (freezing)
70°F =~ 20°C (human-friendly)
100°F =~ 37°C (body)
(212°F) = 100°C (boiling)
350°F = (175°C) (oven)
The values in parentheses are those I had to look up for this post.