Research Report #15 — January Thaws
For many years scientists and naturalists have been studying and observing the flora and fauna of the Shawangunk Ridge. Foremost among them was Daniel Smiley, for whom Mohonk Preserve’s Daniel Smiley Research Center is named. Dan wrote numerous reports summarizing his observations on various topics. This regularly occurring series will feature some of these reports; some hold tremendous scientific value today and just await an interested researcher to follow up, others showcase a quirky sense of humor or highlight an oddity of nature.
Read the report: “January ‘Thaws.” February 1987. Daniel Smiley and Paul C. Huth.
A note from Paul C. Huth, Director of Research Emeritus: This Research Report is in part derived from folklore, and as we said in 1987 when written, January thaws “received little attention in meteorological literature,” but reappears in popular literature almost every year. This thaw is considered a meteorological “singularity” or “anomaly” that occurs on average between January 20 and 23rd, when the day and nighttime temperatures remain above freezing. How often does it occur?
We became interested in the topic as it might relate to our long term species phenological observations. A period of warmth with well above freezing temperatures over several days after winter weather has become firmly established can cause over wintering amphibians to break their dormancy and emerge. Overwintering adult insects can also be spotted.
We used the monthly weather records for the 90 Januarys’ from 1896 to 1985, collected at the Mohonk Lake Cooperative Weather Station, which is part of the National Weather Service. We looked in the records for a period in January between the 16th and the 31st, when the daily maximum temperature reached 40°F or higher for two or more days.
What we found was surprising, in that 64 of the 90 Januarys’, or 71%, showed a thaw during the period. There was no apparent relationship to any precipitation during the thaw, or to the amount of snow on the ground, except during the longer runs, for it’s decrease in depth over time. The longest runs of consecutive days was 12 days, occurring four times-1913, 1916, 1947, and 1973. Maximum daily temperatures in the upper 40s are most common, but temperatures in the mid to upper 50s are not uncommon.
Looking at the more recent January weather for the last 32 years using the same criteria, I found a thaw occurred in 19 years, or 59% of the years. If we tally up the whole 122 year record, 1896 to 2017, 83 of the Januarys’ showed a thaw, or 68% of the years. The 12 day record run mentioned above still holds.
Read the report: “January ‘Thaws.” February 1987. Daniel Smiley and Paul C. Huth.
