The thing about mean!

When you take the daily high temperature and the low, add them together and divide by two you get a mean or average temperature for that day. Values can typically range from a high of 78F (a very hot day in the mid nineties followed by a muggy night in the mid sixties) to a very cold 5F with a typical morning temperature of twenty followed by a frigid night of subzero weather. Brr. At right is mean thermometer showing what you can expect at various mean temperatures.

As we head into the winter season, the mean temperature normally runs somewhere in the mid thirties. December, for instance normally has a monthly mean temperature of 35F. This means people living in southwest Missouri can expect daily highs somewhere in the forties with overnight temperatures falling into the upper twenties. Of course, there will be days when it gets up there into the sixties while some nights might flirt with single digits. But, in general, the range is an average high of 44F for a high and 23F for a low to arrive at a mean temperature of 34 for the three month period December through February (the data courtesy of the National Weather Service for Springfield, Missouri).

A cold winter temperature regime like this can prove to be daunting and costly if your home is either poorly insulated or if your heat source(s) are inefficient. Depending on what type of heating devices you have, it’s a good idea to have them checked on a regular basis. This is especially important if you are running a central system that may be in the form of a split conventional AC setup, a heat pump with one or more stages or a package deal. In my case, I have a two stage heat pump with a single stage cooling capability in a split arrangement. My average cost last year for electricity last year was about $120 at nine cents per kilowatt hour. But thanks to a recent increase of 13%, I expect my heating bills will be even higher. Unless I do something about them that is.

Just what can be done to reduce your electric bills? Well, some of the factors that can help reduce the overall cost include; making sure I have adequate insulation, setting the thermostat to as low as possible (in my case 70F) and making sure that the furnace/heat pump is working as efficiently as possible. That means having it checked for leaks and replacing the filter for a good start.

The other big unknown is just what Mother Nature plans to serve in the way of weather this time around. I’m now hoping Al Gore was right and that we will enjoy a warmer than normal Christmas!

Is a ‘mean temperature’ just bad tempered?

No, actually the word is a meteorological term that refers to the averaging of two or more temperatures. In many cases, it is the result of taking the high and low temperature that occur over a twenty four hour period. It’s an important number for anyone who wants to get a feel for how warm or cold a day was ‘on average’ The term is also used quite often in figuring how many heating or cooling degree days were needed to heat or cool a home or business. One popular approximation method to get this number is to take the average or mean temperature on any given day, and subtract it from the base temperature of 65F. If the value is less than or equal to zero, that day has zero HDD. But if the value is positive, that number represents the number of HDD on that day. Here’s an example:

Let’s assume the high for the day at your location was 54 Fahrenheit and the low was 32F. The average therefore would be (52+32)/2 = 43. We then subtract this from the bas temperature (65) to get a twenty-two degrees. Therefore there were 22 heating degree days (HDD) for that period of time.  Now that I’ve confused you completely, you might want to go to this article on degree days for a good explanation. A wonderful calculation for figuring your degree days for the year is here.

In my research on heating my home for this winter, I’ve developed a rough approximation of how hard my furnace will have to work for the next day by just looking at the mean temperature that is expected. How I arrived at this will be the subject of a future blog.