September weather in Denton County will go into the record books as an exceptionally dry month with two long weeks of summertime temperatures.
The first week of September was marked by clouds and northeast winds on the final, extreme, outer bands of Hurricane Harvey. The western edge of the counter-clockwise circulation brought in cooler air from the Northern plains which resulted in highs in the lower 80’s on the 6th, 7th and 8th. Our coolest overnight low was a teasing 50 degrees on the morning of the 7th, but it wasn’t to last.
Late summer heat returned with highs at or above 90 degrees from September 13th through the 25th. Our hottest temperature was 98 on the 19th. With an average high of 89 and a low of 65, our combined day-night monthly average temperature came out to about 77, which was .7 degrees warmer than normal. Seemed hotter than that, didn’t it?
The heat was aggravated by a mini-drought of nearly 29 rain-free days from August 27th until September 26th, interrupted only by 4/10ths of an inch on September 19th. Three-hundredths fell on the 26th and 27th, while another .09″ fell on the 28th, and the 29th had all of one-tenth of an inch of rain. Total rainfall for the month was .62 inches, which was 2.13″ below normal for September. So far this year, Denton has received about 28 inches of rain. No severe weather was reported during the month.
Looking ahead, there’s no reason to expect any significant change from our warm, dry weather regime in the near future, although October always has the potential for busted forecasts, severe storms and heavy rains.
The period from mid-October to mid-November represents a secondary peak in our severe weather risk across North Texas, due to the southward descent of the Polar jet stream and the resulting clash of warm/humid, cold/dry air masses.
Although no clear trend is indicated, the Climate Prediction Center notes that Pacific Ocean temperatures have fallen slightly below their norms for this time of year, leading to a weak prediction of a La Nina. What does that mean for North Texas? Almost nothing. La Nina winters have been both warmer/drier and also colder/wetter than normal, to the extremes.
Last winter (2016-2017) saw a weak La Nina that left North Texas with its warmest winter on record. DFW recorded only 11 nights at or below freezing and the last actual freeze in DFW was January 8th (‘Freeze-less winters’ have occurred in DFW, but January 8th is the earliest ‘last freeze’ on record.).
By contrast, a previous weak La Nina in the winter of 1967-68 produced a three-inch snowfall in February, 40 freezes and a winter low of 12 degrees. For now, it makes more sense to prepare for warm, dry weather until further notice.
Brad Barton is Chief Meteorologist of WBAP820/570KLIF/99.5 “The Wolf.” Paul Ruekberg of NewsWatch Dallas contributed to this report.