After a record-smashing Friday (80 degrees) a somewhat cooler but still warm airmass will settle across western Nevada. A dry cold front will drop Saturday’s temperatures back into the low 70s and will bring a few clouds to the region, but temperatures rebound into the mid-70s Sunday and again to near 80 degrees on Monday. Another weak and dry cold front will drop our temperatures back into the 60s on Tuesday and keep them there for most of the rest of the work week.

Lee wondered: “Do you know a definition for the Arctic Circle? I have heard two. One is it is above that latitude where the day and night is 24 hrs. The other is it north of the latitude where the hottest average monthly temperature is above 10 degrees.”

Let me take on the second option first. The Arctic Circle has no direct connection to any particular temperature range…although it is certainly cold, and the 10 degrees average temperature line might well be reasonably close to accurate (I really don’t know that for sure, and temperature records are pretty sparse up there.) But the definition has more to do with astronomy than meteorology.

Basically, it is the southern extent of the theoretical “Polar Day”… or the farthest south you can go and still have 24 hours of sun at the summer solstice (or 24 hours of night at the winter solstice, called the “Polar Night”). It’s located at latitude 66.56083 degrees north. This is what you get when you subtract the tilt of the earth (23 degrees and change) from 90 degrees.

If you really want to get picky about it, you can actually go about 56 miles south of the Arctic Circle and still see part of the sun continuously. That’s because of two factors discussed the last few days when we talked about the equinox. Atmospheric refraction and the fact that the sun is a disc and not a single point both allow you to see the top of the sun farther to the south. But the math works out a lot easier to just subtract the earth’s inclination from 90 degrees and establish that as the Arctic Circle.