Average Temperatures

[Billy Griffin]

Okay, newbie question from an old fart... but I'm curious how the climatological data is compiled to determine "average" temperatures.

Here in Seattle, for example; over the past several days, it's been ~ 80 - 90 degrees. "Average" temp claims to be in the 60s for this time of year.

My question is... are these "averages" compiled over an annual basis, or how often are these numbers updated?

Not to start the global warming discussion, but assuming warmer temps are now becoming more common, wouldn't average temps factor into this data?

And over how many years is this data compiled to determine an "average" high and low temperature?

 

[GPhillips]

The average temperatures are computed over a 30 year period. For the climate products that the NWS puts out on a daily basis, the 30 year period for averaging is 1971-2000. In a couple years, that will change to 1980-2010.

 

[Billy Griffin]

Thanks! Elementary question, but I was more curious as to when the next updated averaging would be. Anxious to see what changes occur and in what parts of the U.S. are more affected.