Calculating Average Temperature

[RayProudfoot]

Steve,

I have a web page showing average temperatures for each season. http://www.cheadlehulmeweather.co.uk/seasonaverages.htm

I calculated the average for autumn 2012 by taking the average of the Cumulus average temperature between 1 Sept - 30 Nov. This resulted in an avg temp of 9.7C. But looking at the NOAA avg deviations for Sept, Oct and Nov they were -0.7, -1.0 and -0.1 making it -1.8C colder than average. But the average of averages on my webpage is only -0.6C.

Looking at the calculated average for one date I'm not sure how you are calculating it. For example, on 22/11/12 the max was 13.7, min was 6.7 and the Cumulus average was 9.8. But the mid-way point between those two temps is 10.2.

Could you explain how you calculate the average temp please and why it differs from my calculation. I remember something from my school days that it's unwise to take an average of another average.

[steve]

Could you explain how you calculate the average temp please and why it differs from my calculation.

As described here: http://wiki.sandaysoft.com/a/Average_temperature

[RayProudfoot]

Thanks Steve. That makes sense. It presents me with something of a quandry as I cannot perform the same calculation. Ho hum.

[steve]

I don't really follow what you're trying to do. If you take the average of any set of Cumulus averages, then those average are effectively done by the same method as Cumulus (with perhaps a small rounding error). Could you show the figures that you're using and what you're doing with them? It's possible it's a bug in the Cumulus NOAA report code.

[RayProudfoot]

Hi Steve,

I've discovered my error. There's no problem with your calculations.

I calculated the difference for the 3 average temperatures for Sept, Oct and Nov 2012 - -0.7, -1.0 and -0.1 and added them together but stupidly didn't then divide by 3 to get the average.

If you do that you end up with -0.6 and that is correctly shown on my season average page. http://www.cheadlehulmeweather.co.uk/seasonaverages.htm

So the average for Autumn is 10.3 and the 2012 autumn average is 9.7 - 0.6 below the long-term average I entered into my NOAA temps.

Sometimes you miss the bleeding obvious!