Quick Temperature Conversion from ℃ to ℉ Memorize

Exactly 5C=41F   10C=50F  15C=59F  20C=68F  25C=77F  30C=86F
So I think this is easy to recall:
10C=50F
therefore
5C=40F

5C-40F, 10C-50F, 15C-60F, 20C-70F, 25C-80F--after this it is obvious it is hot out but if you want to be a perfectionist 30C-85F and 35C-100F\ this is the exception here to the rule of 5C=10F yet it is roughly true from 40F (5C) to 80F (25C)

Here is an easy way below 0-C-freezing inF:

-10C=15F  -15=5F  -20C=-5F

It is always so frustrating to get out of the u.s.a. and not see temperatures in Fahrenheit.
Photo from Creative Commons.
I personally cannot find a thermometer marked like this one.

Copy and Paste for you to borrow:
℉ Unicode 2109
℃ Unicode 2103
°  Unicode 00b0 (these are zeroes)