Mild autumn?

Those are heating degree days. They are calculated using a starting point of 65F, assuming that an average house doesnt need any heat above that temperature. then you just add up the degrees below that point for each day of the month.

For example if on day one the average temp for the day is 50, thats 65 - 50 = 15 HDD.
And on day 2, the average temp for the day is 40, that's 25 HDD
And on day 3 the average temp is 60, that's 5 HDD.

You sum those figures up over whatever time period you want.

It hit 70 here today.

How do you know what the average temperature of the day is?

Ave Nov temps at my location:

2012 41°F
2011 50°F
2010 48°F
2009 50°F
2008 45°F

IOW, coldest Nov in memory. This November was colder than the ave temp for last December (42°F).

Some interesting replies in here. Apparently weather truly is local!

There are services that compile this info from meteorological records. I get it from http://www.degreedays.net/

Hm, this site isn't working for me. I can download the data, but it tries to open MS Excel for me to see it and it says there is an error and I can't see anything.

Ok, found a site to get these numbers. This November was very cold here, it was as cold as February, which is usually our 2nd coldest month behind January. November is normally the 4th coldest month behind Jan, Dec and Feb. With these abnormally warm temps we are having this week, I don't think December is going to be able to be colder than November.

Ah, but there are still 27 more days in December; we've only had 4 to much too early for any predictions on colder or warmer.

Today was typical after a warm-up. Kept getting colder as the day progressed. Was working outdoors and thought it was just me but the temperature had dropped more than 10 degrees already by 4:00 or 4:30. Tomorrow I'll probably break out the Carhartts.

Of course now we are jinxed. The 10 day is calling for 60s again.