Brrr

When I left work tonight to go run my circuit, it was 61 degrees according to the big readerboard in the student parking lot. The sun fell behing the horizon as I was running and I could never run fast enough to get ahead of the chill. I just checked the temp on our deck and its 31 degrees out there now - less than 2.5 hours after it was 61. How does the temperature drop like that in these longitudes? I know that in the realm of lego-las, 31 is considered balmy, but I'm afraid I'll flash freeze on my next outing.