As daylight length continues to shorten around these parts as we approach winter, average temperature drops are slow to adjust to the shortening days. September features average highs in the 70's and low 80's, with the drop in average increasing in intensity after September 15th as daylight truly begins to wane. October and November mark the steepest drop in average daily temperature in the course of the year, as average highs drop 22 degrees from September's high average of 78 to November's average of 56.
Over the next several weeks, that drop in average will be relatively quick. Believe it or not, in nine weeks our average high will be 45 degrees! Given the average high today is 69 degrees, that 24 degree drop should serve as a reminder that, yes, winter chill will eventually be on its way...even if the first week of October has been anything but cool.
That drop in average temperature is greater on the high side than the low -- average highs between October 1st and December 31st drop by 31 degrees, while the average low drops 27. You can thank the heat island but short days (less of an opportunity to warm) for the combination the narrows the temperature differential over the course of a day.
You'll notice in the chart above that the average low does not get to 30 degrees until mid December. Two months from today (December 8th) is the first average low of 32 in the cold season. We have a ways to go for the city to reach that level of chill. But it is coming...eventually...and eventually, on a consistent basis.