4th coldest start to the year - Tucson News Now

4th coldest start to the year

Coming off the warmest year on record, Tucsonans were hopefully looking for a different start to the year, maybe a cooler start. That definitely occurred during the 1st half of the month, which goes into the record books as the 4th coldest first 16 days of the calendar year on record. The second half of the month was very warm and goes into the record books as the 10th warmest second half of January on record. So it definitely was a tale of two halves.


Seven of the first 10 days of the month recorded below normal temperatures with daily highs in the 50s and 60s while the lows were mostly in the 30s. In fact, five of the daily lows were at or below freezing through the 10th. In 2012, there was only seven freezing days. Then a Pacific cold front, associated with a strong upper level trough that was over the western states, moved through the area between 11 pm on the 10th and 1 am on the 11th.


The chart shows the temperature and pressure trace at the Tucson International airport for every minute from 11 PM on the 10th to 1 am on the 11th. The area in the red box highlights the time frame when the cold front moved through the Tucson International Airport (between 12:05 am MST and 12:10 am MST). A cold front passage is noted by a temperature fall combined with a pressure rise and wind shift. The high temperature on the 11th (54°) occurred at 12:03 am MST right before the cold front hit the airport. By 1 am MST, the temperature had dropped to 39°.




Rainfall across the metro was rather light with amounts less than a tenth of an inch.

What followed over the next five days was some of the coldest temperatures this area has seen since 1971. The initial cold air mass on the 11th was reinforced by two colder air masses, one on the 12th followed by an even colder air mass on the 14th. Highs in this cold snap were in the mid to upper 40s. A record low maximum (high) temperature was tied on the 15th (47°; old record 47° in 1949). As each day passed, the daily lows just got colder. Lows were in the lower to mid 20s on the 12th and 13th; upper teens to lower 20s on the 14th, then bottoming out in the mid to upper teens on the 15th. The airport established new daily records on the 14th (21°; old record 22° in 1940) and on the 15th (17°; old record 20° in 2007). The 17° low on the 15th is the coldest low the airport has recorded since Christmas Eve 1974 when the low was 16°. This also ranks as the 16th coldest low temperature ever recorded in Tucson (tied with 10 other dates). This year marked the 100th anniversary of the official all-time coldest low temperature recorded in Tucson. The record low of 6° occurred on January 7, 1913. A webpage commemorating this event can be found here.


Some all-time record consecutive day streaks were threatened during this cold snap. They were:

Most consecutive days with daily highs colder than 50°   Most consecutive days with daily lows 25° or colder
1T) 5 days - January 3-7, 1971 1T) 8 days - December 8-15, 1916
1T) 5 days - January 26-30, 1949 1T) 8 days - January 25 - February 1, 1904
1T) 5 days - Dec. 31, 1946 - Jan. 4, 1947 3) 7 days - December 11-17, 1911
4T) 4 days - January 12-15, 2013 4T) 6 days - January 3-8, 1971
4T) 4 days - December 6-9, 1960 4T) 6 days - January 22-27, 1937
4T) 4 days - January 15-18, 1949 4T) 6 days - January 18-23, 1936
4T) 4 days - January 20-23, 1937 4T) 6 days - January 9-14, 1925
4T) 4 days - January 3-6, 1910 8T) 5 days - January 12-16, 2013
The airport stayed below 50° for 131 consecutive hours which is 11 hours shy of the 142 consecutive hours from 1971. 8T) 5 days - February 19-23, 1955
8T) 5 days - December 13-17, 1901
8T) 5 days - December 24-28, 1895

The first sixteen days of January goes into the record books as the 4th coldest on record with an average temperature of 43.5°. The 4-day average temperature of 34° for the 12th through the 15th was the coldest ever for these dates combined and also ranks as the 13th coldest any 4-day period on record for a calendar year.

Time period   Avg. Normal Dep. Time period notes
January 1-16, 2013 High 57.1° 64.8° - 7.7°

4th coldest on record

(1913-41.7°; 1937-41.9°; 1971-42.9°)

Low 29.8° 39.4° - 9.6°
Temp. 43.5° 52.1° - 8.6°
January 12-15, 2013   Avg. Normal Dep. COLDEST on record for these four days; 13th coldest any 4-day period on record
High 46.5° 65.0° - 18.5°
Low 21.5° 40.0° - 18.5°
Temp. 34.0° 52.5° - 18.5°

Temperatures returned to normal by the 17th with the warming trend continuing through the 21st as strong high pressure aloft was over the area. Daily highs were in the upper 70s to lower 80s from the 20th through the 23rd with record highs, yes record highs a week after the record cold snap, being set on the 22nd (81°; old record 80° in 1986) and tied on the 23rd (80°; old record 80° in 1986). One week after Tucson stood as the 4th coldest January to date (16th) on record, a weeks worth of above to much above normal temperatures improved the January ranking to 35th coldest (tied with 1987 & 1975) by the 23rd.


A bit of a surprise on the 24th as light showers developed across the area as subtropical moisture passed through the state. Rainfall amounts were rather light, generally less than a tenth of an inch. What was noteworthy with this event was that the airport set a new daily record high minimum (low) temperature for the date with a low of 56°, which broke the old record of 54° from 2006. This also ranks as the 7th warmest daily low temperature on record for January. The warmest January low temperature on record is 62° set on January 21, 2009.


After a dry day on the 25th where the daily high was in the upper 70s after a morning low near 50°, an abnormally high amount of subtropical moisture for January moved in from the south. Combined with a weather system moving into from off the northern Baja coast, widespread rain developed early on the morning of the 26th and continued into the afternoon hours. Rainfall amounts across the metro area varied widely with 0.20" on the southeast side to over one inch on the north-northwest side. Since this was a warm system, all of the precipitation in the mountains was in the form of rain. Up to 2" fell on the Catalina Mountains and combined with the melting snow pack, runoff from the rain caught hikers in Bear Canyon by surprise. Up to 50 hikers had to be rescued. The airport officially recorded 0.71" of rain, which broke the record for the 26th of 0.67" which occurred in 1985. Additionally, the low temperature of the 26th of 55° set a new daily record high minimum (low) temperature besting the old record of 53° from 2005. This also ranks as the 12th warmest daily low temperature on record for January (tied with twelve other January dates). The three consecutive days with daily lows of 50° or warmer is the third longest stretch on record for January, behind the 6 consecutive days from 2009 (19th to 24th) and 4 days from 1957 (8th to 11th).


The 27th was dry before another cold front, along with valley rain and mountain snow showers, moved through the area around noon on the 28th. Showers continued through the evening of the 28th into the morning of the 29th as the upper level portion of the weather system pushed across the area. Rainfall totals were generally less than two-tenths of an inch with localized higher amounts near a half an inch near Vail and Corona de Tucson.


The remainder of the month remained cooler with normal.


Source: National Weatehr Service

The average monthly temperature of 49.8° is 2.8° below normal and ranks as the 36th coldest January on record. Temperature extremes for the month ranged from a record high of 81° on the 22nd to a record low of 17° on the 15th. The chart below shows the cumulative departure from normal for the average temperature recorded at the airport. Notice that the monthly average temperature bottomed out at 8.6° below normal on the 16th. Thanks to the 10th warmest 2nd half of January on record the average temperature departure from normal improved to 2.8° below normal.

Some miscellaneous January temperature/precipitation notes:

  • 4 days with highs colder than 50°. This is the most since 1971 when there were 5 days. January record is 12 days from 1949.
  • 12 days with lows 32° or colder. This is the most since 1964 when there were also 13 days. January record is 27 days from 1904.
  • For the first time since April 1932, daily records were set in all of the four temperature categories (high, low, low high & high low) plus rainfall. A special webpage was posted on our website for this unique climatic occasion.
Rainfall amounts across the metro area for the month, using several sources like rainlog.org, the Pima County Regional Flood Control District gages and CoCoRaHS, ranged from a four-tenths of an inch to 1.25", with the highest totals occurring on the north-northwest side of the metro area. Over two inches of rain fell across the surrounding mountains. The airport, which is the official recording location for Tucson, recorded 0.81" of rain, which is slightly over a tenth of an inch below normal. This ranks as the 48th wettest January on record, tied with 1930.
January 2012 stats
Average high temperature
- 2.3°
Average low temperature
- 3.3°
Average temperature
- 2.8°
- 0.13"
2012-13 Water Year rainfall (Oct-Jan)
- 1.31"

Winter 2012-2013
Two-thirds of Winter 2012-13 is in the records books with an average temperature of 51.6°, which is eight-tenths of a degree below normal. With one month left in meteorological winter this ranks as the 53rd warmest winter on record. The airport, which is the official recording location for Tucson, has recorded 1.99" of rain which is slightly over a tenth of an inch /0.12"/ above normal and currently ranks as the 40th wettest winter on record.

Looking ahead into February
The Climate Prediction Center forecasts equal probabilities for either below or above normal temperatures and precipitation.
  Daily normals | Daily records
Normal monthly high temperature 68.5°
Normal monthly low temperature 42.2°
Normal average monthly temperature 55.3°
Record high temperature 92° on February 14, 1957
Record low temperature 17° on February 7, 1899
Warmest February (avg.) 61.1° in 1957
Coldest February (avg.) 45.3° in 1903
Normal rainfall 0.86"
Wettest February day 1.26" on February 7, 1966
Wettest February 4.15" in 1905
Driest February 0.00" in 1984/1972/1898
Record February snowfall 4.9" in 1903
The number of daylight hours will increase from 10 hours 41 minutes on the 1st to 11 hours 29 minutes on the 28th, a gain of 48 minutes.
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