The range in daily temperature in New York, also known as diurnal variation, is typically 14 degrees, ranging from 11 degrees in December and January to 17 degrees in May. However, variations by individual day generally range between five and thirty degrees. Variations are affected by atmospheric conditions such as humidity, cloud cover, passage of cold/warm fronts, wind direction and precipitation. What follows are detailed findings about extremes in daily and monthly diurnal temperatures.
- Since 1970, the smallest daily variation has been one degree, which occurred just once, on Dec. 14, 1996 (high/low of 40°/39°). The biggest swing in temperature was 43 degrees back on Jan. 8, 1978 (high/low of 58°/15°).
- Most of the big daily swings in temperature have occurred between January and May. For the purposes of this analysis I chose changes of 33 degrees or more as the qualifier. Swings of this magnitude have occurred 60 times in the past 46 years (thru 2015), an average of 1.3 days per year. 1990 had the most - six days.
- Since 1970, there have been just eight days that experienced a temperature change of 40 degrees or more. The last time it happened was on Dec. 22, 1998, when the temperature plummeted from 63° to 22°.
- By month, the smallest difference between the average high and low occurred in November 1977, when it was only 8.4 degrees (high of 51.5/low of 43.1). The greatest difference between the high/low was 21.2 degrees in May 1994 (high of 72.4/low of 51.2).
- Half of the months with variations less than 11 degrees have occurred since 2001, while just 20% of variations greater than 18 degrees have occurred in this century (the last time was in May 2015 when there was a 19.8 degree variation). This is likely a function of global warming, as overnight temperatures have risen at a faster rather than high temperatures.
- On average, daily temperature variations of two or three degrees occur just a couple of times each year. However, in 1970 there were five such occurrences in a fifteen-day period, between Dec. 11-25. The last time it occurred was on Nov. 13, 2020, when the high/low was 50°/47°.