The University of Arizona

College of Agriculture and Life Sciences

Improving Lives, Communities and the Economy

'Extension Expert' looks at Unseasonably Warm Weather

Although some cooler temperatures may be headed our way... Southern Arizona is still experiencing some unseasonably warm temperatures.

Average highs for early december are in the upper 60s - however we've been seeing 80s, and 70s are expected for next week...

Climate and Geospatial Extension Scientist Jeremy Weiss shares what this unseasonably warm weather could mean.


Are we, in fact, having unseasonably warm weather, for this time of year?

"Yes. At least in Tucson, there have been seven record high temperatures set between November 1 and November 28. Five in-a-row were set between November 23-27, with two of those over 90F. Every day in November has seen minimum and maximum daily temperatures above average. This information is from "

Any speculation on *why* this is happening?

"Part of the reason why is due to meteorological / short-term weather conditions…in this case that would be high pressure over the state/region that keeps cooler air and storm systems away.  Another part of the reason why is due to a long-term warming trend across the region over the past two to three decades, particular with minimum temperatures. I’ve attached a graph showing September-October-November (autumn) minimum temperature for Pima County that illustrates this. (Data are from It’s a similar story for other Arizona counties."

Are we just having this warm weather in Pima County… or are we seeing it across Arizona?

"I’ve seen other data that indicate above-average temperatures during November 2017 in other parts of the state, as well."

From a Cooperative Extension perspective - the goal of which is to take the science of the University, to bear on practical problems -  how is this/how could this weather affect/start affecting farmers and/or crops?

"A couple of potential impacts to agriculture in southeastern Arizona come to mind in the context of the above-average temperatures we have experienced so far this fall. One is the germination of pecans prior to harvest. This is known as vivipary, and can reduce nut quality and thus the price that a grower receives for the crop. I have heard that this is an issue for some growers this fall. Another is the hardening-off of new orchard plantings. For instance, there have been a large number of acres of pistachios planted recently in Cochise County. If warm weather transitions abruptly to cold weather and freezing temperatures without a gradual cooling off period, young trees may not fully harden off and may be susceptible to stem and trunk damage that would decrease tree productivity in subsequent years."