Personally, I think the Flagstaff Airport data is probably tainted by the continuous development over time. The runway was recently lengthed. Additional buildings are constantly going into the area. More parking was added in the late 90s or early 2000′s. All of it can change the heat signal. None the less, here is an interesting graphic from the National Weather Service at Flagstaff. If you dig deeper into what happened over the summer, the story may have been vastly different for you.

Record Flagstaff Growing Season

Many locations had a much shorter season because of two cold spells. First, June 12 was chilly. The airport reported 33 degrees. A Wunderground reporting station, KAZFLAGS22, reported a low of 31.1 degrees. The Grand Canyon reported 32 degrees. Fort Valley reported a low of 27 degrees. This goes to show what the local variability can do.

Second August 8 was a shocker. The airport reported a low of 35 degrees. Many people reported losing some of their gardens on this day. Granted, KAZFLAGS22 reported a low of 34.9 degrees. The Grand Canyon slipped below freezing on August 8. Again, Fort Valley reported a low of about 27 degrees

So, if you don’t live at the airport, your growing season may have been from June 12 to August 8. A mere 57 days and a potential record breaker in the opposite direction. Many efforts are underway to document the effects of local environmental change on temperature records, such as surfacestations.org. I hope you had the long growing season, it was a beautiful summer

Well, I believed this weeks forecasts of cold overnight temps. Instead we had quite a nice week of warm, comfortable days. This weekend will be beautiful. Get out and enjoy it. Might be a good time to harvest the remainder of the garden if we can believe what all of the forecast outlets are saying. Somewhere near the middle of next week, summer should end and fall should move into full swing as a cold system moves through Arizona. Highs may not leave the 50′s. I doubt we will see any precipitation with it.

For some reason, the Shark Oil Barometer is cloudy this morning:

Shark Oil Barometer - 9-25-09

Apparently, the winds overnight inhibited the cooling effect(radiational?) that would have come with the clear skies. The winds should keep going today. Tonight is another chance for a freeze is the winds abate overnight.

Hard to believe that controlled burns are a good idea with the dewpoint in the teens and the winds gusting to 30 miles per hour. Here is the prescribed burn map for Arizona and New Mexico:

Arizona & New Mexico Prescribed Burns

For some in the area, gardens struggle through early August. But for most of Flagstaff we are just now in the middle of the time when the mercury could dip below 32 degrees F. This week is going to bring chilly temperatures. If you live in one of the colder areas, you could see a frost or freeze.

Freezing & Growing Season - NWS Flagstaff

Here is another look at temperature probabilities for the Airport in Flagstaff:

First Freeze Probablity - Flagstaff

But notice what happens just up the road at Fort Valley:

First Freeze Probability - Fort Valley

Notice the curves are steeper and earlier. Take care and watch the forecast for the next few days if you want your garden to last a little longer.