Calculating average temperatures gives you a more accurate picture of the temperature in a specific location than a single measurement ever could. Temperatures fluctuate throughout the day, over the course of a week, month to month and year to year, as well as varying substantially depending on where exactly you are. Making sense of this and coming up with one figure for your purposes requires calculating the mean temperature, which is a specific type of average. You do this by adding up all of your individual measurements and dividing by the number of measurements.
TL;DR (Too Long; Didn't Read)
Calculate the average temperature from several temperature measurements using the formula:
Average temperature = sum of measured temperatures ÷ number of measurements
Where the sum of measured temperatures is found by adding up every measurement. Ensure that all of the measurements are in the same temperature unit before applying this formula. Convert from Celsius to Fahrenheit or vice-versa using the following expressions:
Temperature in Fahrenheit = (Temperature in Celsius × 1.8) + 32
Temperature in Celsius = (Temperature in Fahrenheit – 32) ÷ 1.8
Decide What You Want the Average Of
Plan your calculations based on what exactly you want to work out. Do you want the average temperature for the week in one location, for the day over multiple locations or something else? The calculations are essentially the same in most cases, but this determines what data you need to collect for the calculation.
Take Your Measurements or Obtain Your Data
Take your measurements or find the data you need from an online source. (For example, the National Centers for Environmental Information has data for the U.S. See Resources for a link.) If you’re looking for data to determine the average temperature for the week, you can collect data each day (preferably at the same time in the day in the same location), but if you’re looking for data covering a longer period or over a larger area, it will probably be easier to use existing data.
Convert the Data Into the Same Unit
Celsius, Kelvin and Fahrenheit all express temperature, but all of your data has to be in the same unit if you want to calculate the average. To convert from Celsius to Kelvin, simply add 273 to the temperature in Celsius:
Use the following formulas to convert from Celsius to Fahrenheit or vice-versa:
Add Up Your Individual Measurements
Start calculating your average by taking the sum of your individual measurements, all in the same unit of temperature. Imagine you have the following data for measurements taken over a week, all in degrees Fahrenheit: 70, 68, 79, 78, 73, 69 and 72. Take the sum as follows:
Divide by the Number of Measurements
Divide the total from the previous step by the number of measurement to find the average temperature. In the example, there were seven measurements taken, so you divide by 7 to find the average:
The result from the previous step gives:
Expand this approach as needed for other situations. For example, you can take an average of measurements taken at different times in the day or at different locations to find the average temperature for each day. Then you can find the mean of these results to come up with an average temperature for the whole week.