By Chance E. Gartneer Updated Mar 24, 2022
Guasor/iStock/GettyImages
If you suspect that local climate patterns have shifted, calculating the mean annual temperature provides a clear, objective benchmark. The mean annual temperature is the average of a region’s daily highs and lows over a full year, and it is a cornerstone metric for assessing long‑term climate trends.
To find an average, sum all values and divide by the count. For example, (3 + 6 + 7 + 4) = 20; 20 ÷ 4 = 5.
Record the temperature at each hour for a 24‑hour period—starting at midnight and ending at 11 p.m. Sum the 24 hourly readings and divide by 24. The result is the mean temperature for that day.
Sum the mean daily temperatures for every day in the month. Divide that sum by the number of days in the month (31 for January, 28 or 29 for February, etc.) to obtain the monthly mean.
Sum the 12 monthly means and divide by 12. This value is the mean annual temperature for the year. For more precision, you can average all 365 (or 366) daily means instead of monthly averages.
Different climates can share the same mean annual temperature. A region with mild year‑round temperatures may match a place with extreme seasonal swings. The mean annual temperature is a useful, but not exhaustive, indicator of climate behavior.
For quick calculations, average the daily high and low. For detailed analyses, use all daily data points.
