Americans struggle with metric measurements because, rather than adapt them, they always want to make detailed conversions. It would just be easier to junk the non-metric system and think in metric terms. Why do we even bother with Fahrenheit when we can just use some simple guidelines for determining our relationship to the temperature?
Most people know that 0° C is freezing and 100° C is boiling. We don't need to convert these to 32° F and 212° F because freezing and boiling are our reference points.
Here are some other points.
20° C - a comfortable room temperature. Don't set you winter heating above this.
25° C - a comfortable summer day. Don't set your air-conditing below this.
30° C - a warm summer day, a nice temperature to work outside or to swing in the hammock.
35° C - a hot summer day. Find some shade.
40° C. A very hot summer day. A good sauna temperature for those who don't like a really hot sauna. Others may prefer higher points up to 105°.
Going the other way:
15° C - a cool summer day. You may want to wear a sweater or light jacket.
10° C - a chilly day, You will want to wear a sweater and a light jacket.
5° C - a cold day. You may want to wear gloves, too.
0° C - freezing. Of course you'll wear a medium or heavy jacket and gloves.
-5° C - A brisk winter day. If you work hard, you'll be glad you dressed in layers.
-10° C - Still bearable for being outside, but watch for discomfort.
-15° C - If you don't have to be outside, don't.
-20° C - Keep your car in a garage or have a plugged-in engine block heater.
-40° C - The same level of cold as in another system. Stay inside.
