CONVERSIONS USING THE
DOMINANT TEMPERATURE SCALES
 
METEOROLOGIST JEFF HABY
To interpret the
analysis and
forecast charts it is
important to have a thorough understanding of the Celsius
temperature scale. Most of the U.S. population is more familiar with the Fahrenheit temperature scale as compared
to the Celsius temperature scale. This is a disadvantage because most weather data (especially upper air data) is
in degrees Celsius. Until we see the wonderful day when the Fahrenheit scale is abolished and all temperature records
are changed to degrees Celsius, it is important to be able to
convert degrees F to degrees C and vice versa. People
who are more familiar with the Fahrenheit temperature scale understand with more clarity how a temperature of 50
degrees F or 100 degrees F feels, but do not have the understanding for how a 17 degrees C temperature or a 32
degrees C temperature feels unless they convert the Celsius temperature to Fahrenheit. Memorizing the Celsius and
Fahrenheit equation can be cumbersome. It would be more beneficial and less time consuming to be able to think of
a Celsius temperature and have the value for Fahrenheit pop right in our head without getting out a calculator and
doing the math. Well, there is a method that can approximate a Fahrenheit temperature from a Celsius temperature
without doing the math. The method involves knowing a few key temperatures and knowing that there are about 2 degrees
Fahrenheit in 1 degree Celsius. First, write down these following 6 values and memorize them:
10 C = 14 F
0 C = 32 F
10 C = 50 F
20 C = 68 F
30 C = 86 F
40 C = 104 F
After memorizing these 6 values, you can interpolate the
Celsius temperature to get an approximate Fahrenheit temperature. For example, if a 850 chart has a 15 degrees C
isotherm, this can be converted into the Fahrenheit temperature in your head since you know that 15 is half way between
10 and 20, therefore 59 is halfway between 50 and 68. Therefore the Fahrenheit temperature is 59 degrees. As a
second example, suppose a temperature of 7 C is given. You have memorized that 10 C is 50 F, the difference between
10 and 7 is 3 degrees C which is equal to a change of 6 degrees F (remember there are about 2 degrees F in a 1 degree
C temperature change), therefore the Fahrenheit temperature is 50  6, which is 44 F. With this technique, practice
makes perfect.
As a side note: Although when using whole numbers the Fahrenheit scale is a more precise temperature
scale, current instrumentation is precise enough to report temperatures to a tenth of a degree Celsius (a tenth of a
degree Fahrenheit is bordering on being too precise unless big money is spent). This will help define more precisely
when surface temperatures will rise above or fall from the freezing point and will allow a finer resolution of
mesoscale temperatures and temperature changes over a region. Perhaps someday, with a wide distribution of new precise
temperature sensors, surface observations in the U.S. can be reported in 10ths of a degree Celsius (examples: the
temperature outside right now is 15.7 degrees C, the temperature is 0.3 degrees C). This kind of change may be too
radical for the general public to handle (U.S. has not even been able to convert to the metric system) and who will
be able to tell the difference between 12.3 and 12.8 degrees C. This could be a marketing tool however: "our station
and weather watchers have the most accurate and precise temperature sensors in the market".


