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August 2012 climate report for Tucson Arizona
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August 2012 climate report for Tucson

Headlines
4th hottest and 28th driest August on record
9 straight days of 105° or hotter, 2nd longest August streak on record
Five daily August records set or tied
6th hottest and 31st wettest Summer on record
 

When the Climate Prediction Center issued their zero lead time forecast for August on July 31st, it called for enhanced probabilities for above normal temperatures and slightly enhanced probabilities for above normal rain. The temperature forecast was right with the airport recording the 4th warmest August on record. Looking back at the historical records dating back to 1895 and using the 1981-2010 normals, only 14 August's recorded above normal rainfall following an above normal July. The last such occurrence was in 2006 when the airport recorded 5.40" in July and 3.01" in August.

 

While most of the 2nd half of July was cooler than normal, the first half of August was warmer than normal with highs between 100 and 109 degrees. Record highs were set/tied on the 8th, 12th, 13th and 14th. (see table below). Total rainfall across the metro area during the first half of the month showed higher amounts over an inch occurred from midtown to the foothills, with less than a half an inch across southern portions of the metro area. The airport recorded only 0.17" during the first half of the month. Historically, at the official recording spot in Tucson, the first half of August 2012 goes into the record books as the 14th driest on record.

         
Record type Date Record Previous Year(s)
High minimum Aug. 8 82° (tied) 82° 1980
High Aug. 8 108° 107° 1995
High Aug. 12 109° 108° 1993
High Aug. 13 109° 106° 1996/1994/1962
High Aug. 14 106° (tied) 106° 1994/1988/1898
 

Daily thunderstorm activity increased during the next 12 days resulting in most of the area recording 1"-3" of rain. However, there were areas that recorded less than a half an inch.

 

Drier air moved in from the east during the last four days of the month, resulting in little thunderstorm activity.

 

Temperature extremes for the month ranged from a high of 109 degrees on the 12th & 13th to a low of 71 degrees on the 22nd. Triple digit temperatures were recorded on 20 days, which is the 5th most in August (tied with 1989 & 1915) on record. The record is 30 days from 1994. The airport recorded a string of nine straight days where the high was 105° or hotter, which is the second longest August streak on record. The record is 10 straight days, which occurred in 1995 (1st thru 10th). This also ranks as the 15th longest calendar year streak on record. For the first time since 1994, the airport recorded back-to-back August days where it was 109° or hotter. Overall, the monthly average temperature of 88.2° is almost three degrees above normal and ranks as the 4th HOTTEST August on record. Tucsonans should take comfort that August 2012 was one degree cooler than 2011 which was the 2nd HOTTEST August on record.

 
August 2012 daily high temperature departure from normal August 2012 daily low temperature departure from normal
Click on image above for larger view
 

As is normally the case during the summer thunderstorm season, rainfall amounts varied widely across the metro area. Using several sources like rainlog.org, the Pima County Regional Flood Control District gages and CoCoRaHS, rainfall amounts for the month generally ranged from one inch to three inches with very localized amounts between 4"-5". The International airport, which is the official recording location for Tucson, was on the low end recording only 1.17" which is 1.22" below normal and ranks as the 28th driest August on record.

 
August 2012 stats
Month
Normal
Departure
Average high temperature
100.5°
97.4°
+ 3.1°
Average low temperature
75.8°
73.3°
+ 2.5°
Average temperature
88.2°
85.3°
+ 2.9°
Number of 100° + highs
20
14
+ 6
Rainfall
1.17"
2.39"
- 1.22"

Summer 2012
 

The forecast for summer 2012, issued by the Climate Prediction Center back in mid-May, called for greatly enhanced probabilities for ABOVE normal temperatures and equal chances of either above or below normal precipitation. Hot is was with above normal rainfall.

 
Summer 2012, which was a half a degree cooler than 2011, goes into the record books as the 6th HOTTEST summer on record with an average temperature of 87.2°. Temperature extremes ranged from 109° on August 12th and 13th to a low of 62° on June 7th. For the first time since 1975 and for only the 7th time dating back to 1895, the hottest summer temperature occurred only in August. The hottest temperature in June was 108° (22nd) while in July it was 105° (1st, 9th & 10th). The other years that saw the hottest summer temperature occurring only in August were 1962, 1950, 1938, 1918 & 1915.
 
Summer 2012 daily high temperature departure from normal Summer 2012 daily low temperature departure from normal
Click on image above for larger view
 

Rainfall amounts across the metro area for the summer season, using several sources like rainlog.org, the Pima County Regional Flood Control District gages and CoCoRaHS, varied widely and ranged from two to ten inches. Officially, the airport recorded 5.64" which is eight-tenths of an inch above normal and goes into the record books at the 31st wettest summer on record.

 
Summer 2012 stats
Season
Normal
Departure
Average high temperature
100.4°
99.1°
+ 1.3°
Average low temperature
74.1°
72.3°
+ 1.8°
Average temperature
87.2°
85.7°
+ 1.5°
Number of 100° + highs
58
51
+ 7
Rainfall
5.64"
4.84"
+ 0.80"
 

2012

The 6th HOTTEST summer on record pushed the average yearly temperature to 72.9° which is 1.7° above normal and ranks as the 6th warmest year to date on record. The average high temperature of 87.4° through the end of August ranks as the 4th warmest on record and well behind the record of 89.3° from 1989. The average low temperature of 58.4° through the end of August ranks as the 6th warmest on record (tied with 1986). 2012 rainfall totals, using several sources like rainlog.org, the Pima County Regional Flood Control District gages and CoCoRaHS, vary widely across the metro area ranging from four to nearly twelve inches. At the beginning of summer, the 0.68" the airport had recorded for the year ranked as the 8th driest to date. By July 20th, when the airport recorded 4.41" for the summer to date, the yearly ranking stood at 34th wettest year to date. The airport only recorded 1.23" for the remainder of the summer with the yearly ranking on August 31st standing as the 41st driest on record with 6.32"

 
2012 stats thru August
Year
Normal
Departure
Average high temperature
87.4°
85.1°
+ 2.3°
Average low temperature
58.4°
57.2°
+ 1.2°
Average temperature
72.9°
71.2°
+ 1.7°
Number of 100° + highs
67
55
+ 12
Rainfall
6.32"
7.91"
- 1.59"
2011-12 Water Year rainfall (Oct-Aug)
9.38"
10.30"
- 0.92"
 

 
Looking ahead into September
The Climate Prediction Center forecasts enhanced probabilities for ABOVE normal temperatures and rainfall.
  Daily normals | Daily records
Normal high temperature 94.5°
Normal low temperature 68.6°
Normal monthly temperature 81.6°
Record high temperature 107° on September 1, 1993
(last of 9 occurrences)
Record low temperature 43° on September 26, 1913
Warmest September (avg) 84.8° in 2000
Coldest September (avg) 76.3° in 1964
Normal rainfall 1.45"
Wettest September day 2.85" on September 10, 1964
Wettest September 5.11" in 1964
Driest September 0.08" in 1953
The number of daylight hours will increase from 12 hours 48 minutes on the 1st to 11 hours 52 minutes on the 30th, a loss of 56 minutes.
 
Looking ahead into Fall 2012
The Climate Prediction Center forecasts slightly enhanced probabilities for ABOVE normal temperatures and enhanced probabilities for ABOVE normal rainfall
   
Normal high temperature 84.2°
Normal low temperature 57.3°
Normal seasonal temperature 70.8°
Warmest Fall (avg.) 74.0° in 1999
Coldest Fall (avg.) 66.0° in 1972/1923/1919
Normal Fall rainfall 3.33"
Wettest Fall 10.97" in 1983
Driest Fall 0.18" in 1953
The autumnal equinox, otherwise known as the beginning of fall, will occur on September 22nd at 7:49 AM MST when the sun begins to cross the equator into the southern hemisphere.
 
Glueck

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