For the purposes of this analysis, I've gathered together months that had their coldest and warmest temperature one or two days apart. On average, this has happened about once every two-and-a-half years. The difference between the coldest and warmest reading has been, on average, 42 degrees (ranging between swings of 29 and 61 degrees). I've limited the months in this analysis to those with "solo" occurrences, i.e., months in which the hottest and coldest temperature occurred on just one date. Through March 2022, there were 58 months that met this criterion. The last time it happened was in Nov. 2009, when the month's coldest temperature occurred on 11/7 (35°), and mildest reading on 11/8 (69°). Here are a few other observations:
- By month, February has had the most instances (nine), while September had the fewest (one). By season, winter has had 20 such months, spring and summer have each had 14, and fall has had 10 months.
- Although the average time between occurrences has been 2-1/2 years, in 1961 it happened in consecutive months (May and June). And there have been three instances in which this type of month was just a month apart from the other: Oct./Dec. 1871; Dec. 1882/Feb. 1883; and Aug./Oct. 1894. (There are no instances in which a month's temperature extremes occurred on the same day).
- We're presently in the midst of the longest hiatus, which started in December 2009. This is in contrast to the 15-year period between 1887-1901 when there were 13 months which had their warmest and coldest readings 1-2 days apart. (Including five consecutive years, 1891-1895.)
GREATEST SWINGS IN A MONTH'S WARMEST-COLDEST TEMPERATURE WHEN 2 DAYS APART
> March 1987/ 61 degrees/ from 76° to 15°
> March 1988/59 degrees/ from 17° to 76°
> Dec. 1871/ 57 degrees/ from -2° to 55°
> Feb. 1967/ 56 degrees/ from 4° to 60°
> April 1880/ 54 degrees/ from 26° to 80°
GREATEST SWINGS IN A MONTH'S WARMEST-COLDEST TEMPERATURE WHEN 1 DAY APART
> Jan. 1934/ 52 degrees/ from 58˜ to 6°
> Jan. 1913/ 45 degrees/ from 18° to 63°
> June 1961/43 degrees/ from 96° to 43°
> Feb. 1947/ 43 degrees/ from 50° to 7°
Finally, there have been nine months in which the temperature extremes occurred on the first and last day of the month, most recently in June 2009.