Not going to confirm this one yet, as there are are ~4 weeks’ more readings still to come – in the coldest part of the year in the Northern Hemisphere – which I expect will drag the annual mean temperature down somewhat.
However, using the data to the first week of December, we get:
rmw42@pandora:~/NOAA$ cat Averages.txt Average-2009.txt | sort | ./warm5-2009 3665 stations had 2009 as one of their 5 warmest years 1906 stations did not have 2009 as of their 5 warmest years 11771 stations rejected for having insufficient data
which shows the proposition to be true in 66% (i.e. near enough two thirds) of stations for now, though if the December average is something like 10F colder than the summer this could change substantially.
It also shows a potential flaw in my “>=90% of days” check – a year can miss out almost an entire month and still be “OK”. That month could just as easily be July as January, and so could move temperatures up or down. I believe missing days will be somewhat randomly distributed, but this should be checked.