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July 2009 climate report for Tucson
 
July 2009 headlines Decade of 2000s headlines
3rd warmest July on record Warmest July decade on record
Summer rains fizzle at the end of month 3rd wettest July decade on record
4th warmest January-July period on record
 
Very warm temperatures, fickle monsoonal flow and severe storms highlighted the weather during July 2009.
 
The month started off like June ended, with below normal daytime temperatures (readings in the mid to upper 90s through the 4th) and monsoonal flow in place. Severe thunderstorms hit the area on the 2nd with flash flooding occuring on the far southeast side on the 4th. Daytime temperatures finally stayed above 100° starting on the 5th with scattered thunderstorms impacting the area through mid-July. Severe thunderstorms once again hit the area on the 7th and 10th along with locally heavy rain which produced localized flash flooding.
 
The summer rains fizzled out during the second half of the month as high pressure aloft, normally near the four corners area during the latter part of July, was displaced further south which kept deep moisture to our south. Daytime high temperatures responded to the stronger high overhead with daytime readings above 100 degrees. The exception was on the 23rd through the 25th where a bit more moisture moved in, which led to scattered showers and thunderstorms and high temperatures in the upper 90s. The month ended up hot as deep monsoonal moisture was scoured out of the area.
 
July 2009 goes into the record books as the 3rd warmest July on record with an average monthly temperature of 90.1 degrees, which is 3.6 degrees above normal. This also ranks as the 4th warmest calender month on record. The average monthly low temperatures of 77.6 degrees goes into the record books as the warmest on record for July and also the warmest for a calendar month.
 
Warmest average
July temperatures
Rank Avg Year
1 90.6° 2005
2 90.4° 1994
3 90.1° 2009
4 89.9° 1989
5 89.7° 1942
 
Warmest calendar
months
Rank Avg Year
1 90.6° Jul 2005
2 90.4° Jul 1994
3 90.2° Aug 1994
4 90.1° Jul 2009
5 89.9° Jul 1989
 
Warmest average
July low temperature
Rank Avg Year
1 77.6° 2009
2T 76.9° 2006
76.9° 2005
4 76.3° 1996
5 76.0° 2007
 
Warmest average
low temperature calendar months
Rank Avg Year
1 77.6° Jul 2009
2T 76.9° Jul 2006
76.9° Jul 2005
4 76.5° Aug 1994
5 76.3° Jul 1996
 
Starting on the 10th and continuing until the end of the month, a streak of 22 consecutive days, each daily low temperature was 75 degrees or warmer. This easily eclipsed the old record of 18 consecutive days set in 2006 and in 2003. The table below lists the top 5 longest streaks.
 
Longest streaks with low temperature of 75 degrees or warmer
Rank # of days Year/Dates Average low temperature
1) 22 2009 (7/10-31) 78.9°
2T) 18 2006 (7/9-26) 80.6°
18 2003 (6/28-7/15) 77.8°
4T) 17 2007 (7/2-18) 79.8°
17 2005 (7/13-29) 79.1°
 
Temperature extremes for the month ranged from a high of 109 degrees on the 19th to a low of 68 degrees on the 4th. Two daily record temperature were set during July. The high of 109 degrees on the 19th broke the previous record of 108 degrees which occurred in 1989, 1978 and 1920. The low temperature of 80 degrees on the 30th tied that dates record previously set in 1993, 1907 and 1906.
 

As is normally the case during July, rainfall totals were highly variable across the area as they ranged from around one inch to four and a half inches, with the highest amounts occurring near the Tucson mountains and up in Oro Valley. Officially, the International airport recorded 1.78" of rain, which is about three-tenths of an inch below normal. This is the first July since 2005 that the airport recorded below normal rainfall.

 
July 2009 stats
Month
Normal
Departure
Average high temperature
102.5°
99.6°
+ 2.9°
Average low temperature
77.6°
73.4°
+ 4.2°
Average temperature
90.1°
86.5°
+ 3.6°
Number of 100+ degree highs
24
17
+ 7
Rainfall
1.78"
2.07"
- 0.29"
 
2009 stats thru July
Year
Normal
Departure
Average high temperature
85.3°
82.6°
+ 2.7°
Average low temperature
56.8°
53.8°
+ 3.0°
Average temperature
71.0°
68.2°
+ 2.8°
Number of 100+ degree highs
42
36
+ 6
Rainfall
4.12"
5.51"
- 1.39"
2008-09 Water Year rainfall (Oct-July)
5.44"
8.42"
- 2.98"
       
The first half of 2009 goes into the records books as the 4th warmest on record with an average temperature of 71.0 degrees. The warmest January to July period occurred in 1989 when the average temperature was 71.5 degrees. The 2008-2009 water year rainfall total at the airport is nearly three inches below normal. This ranks as the 24st driest water year to date.
 
July decade in review: the 2000s

The month of July during the decade of the 2000s will go into the record books as the warmest and 3rd wettest decade on record (dating back to the mid-1890s). The decadal average temperature of 88.0 degrees is seven-tenths of degree warmer than the 1990s. Thanks to the 5.40" in 2006 and 5.22" in 2007, the 5th and 6th wettest July's on record respectively at the airport, the average decadal precipitation of 2.51" was the wettest July decade since the 1950s.

Decadal average temperatures
2000s 1990s 1980s 1970s 1960s 1950s 1940s 1930s 1920s 1910s 1900s
88.0° 87.3° 86.8° 86.0° 85.7° 86.2° 87.1° 86.6° 86.2° 84.4° 85.6°
Decadal average precipitation
2000s 1990s 1980s 1970s 1960s 1950s 1940s 1930s 1920s 1910s 1900s
2.51" 1.81" 2.34" 2.15" 2.13" 3.16" 1.69" 1.46" 1.93" 2.84" 2.29"
 

2005 (90.6°), 2009 (90.1°) and 2003 (89.2°) are ranked as the 1st, 3rd and 6th warmest July's on record respectively. As mentioned above, 2006 (5.40") and 2007 (5.22") ranks as the 5th and 6th wettest July's on record respectively.

Year-by-year statistical recap for Tucson International airport
Year Avg. high Avg. Low Avg. Temp Precip.
2000 101.0° 75.3° 88.2° 1.59"
2001 97.4° 74.9° 86.2° 1.09"
2002 99.1° 74.5° 86.8° 2.47"
2003 102.5° 75.9° 89.2° 2.50"
2004 99.9° 73.7° 86.8° 0.86"
2005 104.2° 76.9° 90.6° 0.72"
2006 99.7° 76.9° 88.3° 5.40"
2007 99.8° 76.0° 87.9° 5.22"
2008 96.9° 74.3° 85.6° 3.42"
2009 102.5° 77.6° 90.1° 1.78"
2000s avg. 100.3° 75.6° 88.0° 2.51"
1971-2000 normal 99.6° 73.4° 86.5° 2.07"
Click on a year for full climate report previously posted.
 

The first two graphs below shows the daily departure from normal, or periods of warm/cold, for each July day from 2000 through 2009. The third graph is the departure from normal for the monthly average temperatures. The fourth graph is the departure from normal for the monthly rainfall. (all years compared against 1971-2000 normals except 2000/2001 which were compared to 1961-1990 normals).

[Daily highs] [Daily lows] [July average temperatures] [July precipitation]
Move your mouse over the locations to change graphics. Click link for larger view.
July graphics
 

Temperature extremes for the decade ranged from 111 degrees on July 17, 2005 and July 2, 2001 to 62 degrees on July 2, 2004. Twenty-five record temperatures were set/tied this past decade (listing below is in chronological order).

Record type Date Record Previous Year(s)
High Minimum July 28, 2000 83° 82° 1979
High July 2, 2001 111° (tied) 111° 1994/1907
Low July 14, 2002 65° (tied) 65° 1962
Low Maximum July 27, 2002 82° 85° 1975
High July 16, 2003 110° 108° 1998/1997/1925
High Minimum July 21, 2004 82° (tied) 82° 1932
High Minimum July 22, 2004 84° 81° 1996
High July 6, 2005 109° (tied) 109° 1989
High July 12, 2005 110° 109° 1994/1985/1925
High Minimum July 13, 2005 86° 85° 1940
High Minimum July 17, 2005 85° 82° 1997
High July 17, 2005 111° 109° 1992
High Minimum July 21, 2005 82° (tied) 82° 2004/1932
High July 21, 2005 108° 107° 1931
High July 21, 2006 110° 108° 2005
High Minimum July 22, 2006 89° 84° 2004
High July 22, 2006 108° 107° 1994/1987
High Minimum July 23, 2006 85° 82° 1943/1932
Low July 31, 2006 66° (tied) 66° 1955/1921/1905
High Minimum July 5, 2007 87° 83° 1953
High Minimum July 6, 2007 87° (tied) 87° 1925
Low Maximum July 10, 2008 86° (tied) 86° 1930
Low Maximum July 11, 2008 89° (tied) 89° 1992/1949/1919
High July 19, 2009 109° 108° 1989/1978/1920
High Minimum July 30, 2009 80° (tied) 80° 1993/1907/1906
 
Two rainfall record were set during the 2000s
Date Record Previous / Year (s)
July 11, 2008 1.73" 0.90" / 1919
July 31, 2006 1.90" 1.43" / 1955 & 1921
 
Looking ahead into August
The Climate Prediction Center forecasts, due to strengthening of El Niño, enhanced probabilities of above normal temperatures and enhanced probabilities for below normal precipitation.
   
Normal high temperature 97.4°
Normal low temperature 72.4°
Normal monthly temperature 84.9°
Record high temperature 112° on August 1, 1993
Record low temperature 55° on August 20, 1917
Warmest August (avg) 90.3° in 1994
Coldest August (avg) 80.8° in 1923
Normal rainfall 2.30"
Wettest August day 2.88" on August 1, 1935
Wettest August 7.93" in 1955
Driest August 0.08" in 1924
   

The number of daylight hours will increase from 13 hours 42 minutes on the 1st to 12 hours 51 minutes on the 31st, a loss of 51 minutes.

 
Glueck

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