Phoenix Shatters Records: Warmest February/Winter and Mind-Boggling March

[GaWx]

1 hour ago, frontranger8 said:

Are we gonna talk about how Fairbanks had their coldest DJFM on record, and shattered their coldest March on record by over 3 degrees?

The contrast sure is fascinating! Anchorage also is getting their coldest March on record. Because this thread is centered on Phoenix, I talked about the record cold Fairbanks in another thread, including in this post:

 

[GaWx]

 From outspoken pro met. Chris Martz fwiw:

 Any comments?

[LongBeachSurfFreak]

Not a very good example. FOK was more of a microclimate, if it's even a legit measurement. It was lower than any other location, regardless of rural/urban location, for hundreds of miles. Nothing lower until deep into New England. It was like 5F colder than even the coldest personal weather stations on Long Island.

It’s a legit ob from an ASOS station.
As far as a micro climate sure. It’s in the heart of the dwarf pine barrens which is characterized by extremely sandy soils and radiates better then any non deep valley location on the east coast.
Regardless of KFOK, KJK was almost 10 degrees cooler then the park or KLGA.


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[donsutherland1]

11 hours ago, GaWx said:

 From outspoken pro met. Chris Martz fwiw:

 Any comments?

Bad methodology. Notice he uses MT and WY. 90s in March are virtually assured to be near or at zero. Thus he assures himself the kind of conclusion he seeks. A more robust approach would involve standardized measurements, e.g., the number of highs 1 sigma, 2 sigma, etc., above the 20th century baseline. 

[chubbs]

52 minutes ago, donsutherland1 said:

Bad methodology. Notice he uses MT and WY. 90s in March are virtually assured to be near or at zero. Thus he assures himself the kind of conclusion he seeks. A more robust approach would involve standardized measurements, e.g., the number of highs 1 sigma, 2 sigma, etc., above the 20th century baseline. 

Another issue: the shelters 100 years ago were not aspirated. Inadequate or poorly sited shelter ran warm. With his number of days metric easy for one or two sites with bad data to bias the result. We saw that in the Chester county, where spuriously warm data from Phoenixville in the 1930s and 1940s biased the >95F day data, by providing the overwhelming majority of the County 95F+ days in that period. 

Better to show the data for every station like chart below. That way a few bad apples don't skew the data. Threadx cities plotted below have the longest climate records.

[GaWx]

1 hour ago, donsutherland1 said:

Bad methodology. Notice he uses MT and WY. 90s in March are virtually assured to be near or at zero. Thus he assures himself the kind of conclusion he seeks. A more robust approach would involve standardized measurements, e.g., the number of highs 1 sigma, 2 sigma, etc., above the 20th century baseline. 

Thanks, Don. He also said “I may look at March days with maximum temperatures at or above the 90th percentile for better measure.”

 If he actually does this and posts it, would that be a better approach? 

[TheClimateChanger]

1 hour ago, chubbs said:

Another issue: the shelters 100 years ago were not aspirated. Inadequate or poorly sited shelter ran warm. With his number of days metric easy for one or two sites with bad data to bias the result. We saw that in the Chester county, where spuriously warm data from Phoenixville in the 1930s and 1940s biased the >95F day data, by providing the overwhelming majority of the County 95F+ days in that period. 

Better to show the data for every station like chart below. That way a few bad apples don't skew the data. Threadx cities plotted below have the longest climate records.

Also, the afternoon/early evening observation time common at the cooperative sites in the earlier decades often tacks on an additional day at or above a threshold temperature to warm spells, since the set temperature for the following day would be only a little bit colder than the daily high.

[donsutherland1]

2 hours ago, GaWx said:

Thanks, Don. He also said “I may look at March days with maximum temperatures at or above the 90th percentile for better measure.”

 If he actually does this and posts it, would that be a better approach? 

Yes. That would be better. The instrument details mentioned by @chubbs could still play a role at some sites.

[donsutherland1]

Powered by a monster heat dome that would be a rarity during the summer, Phoenix and the Southwest experienced mind-boggling warmth during March. 

Chart 1: Daily Temperatures:

Chart 2: Return Time of Monthly Mean Temperature (Historic Period):

The warmth has been persistent since December. December, February, and March set new records for warmest December, February, and March on record. As a result, Phoenix also experienced its warmest December-March period by a large margin.

 

[donsutherland1]

Phoenix was so warm during March 2026 that its mean monthly low, mean monthly high, and mean monthly temperatures would all have ranked second hottest on record for April. Numerous March temperature records surpassed the most extreme values experienced during April.

 

 

[Stormchaserchuck1]

Good stuff Don. +4.2F over DJFM number 2 is amazing stuff. 

[Stormchaserchuck1]

I plotted from Don's warmest DJFM Phoenix years.. it's surprising that the DJFM that occurred a year later is cold in the SW. It has historically snapped back the following year.