Average Monthly Temperature and Precipitation data for Tucson

Average
Monthly Temp
 Month 
Average
Max Temp
 Average
Min Temp
 Difference
 Precipitation
52
 Jan
 64
 39
 25
 0.99
55
 Feb
 68
 42
 26
 0.88
59
 Mar
 73
 45
 28
 0.81
66
 Apr
 82
 50
 32
 0.28 (see note 2)
74
 May
 90
 59
 31
 0.24
84
 Jun
 100
 68
 32
 0.24
86
 Jul
 100
 73
 27
 2.07 (see note 3)
85
 Aug
 97
 72
 25
 2.30
81
 Sep
 94
 68
 26
 1.45
70
 Oct
 84
 57
 27
 1.21
59
 Nov
 72
 45
 27
 0.67
52
 Dec
 65
 39
 26
 1.07 (see note 4)

Notes
1.   Monthly average temperatures are plotted here.  To determine the annual mean temperature add the twelve monthly average temperatures and divide by 12.  You can get a pretty good estimate of the annual mean temperature by adding the highest and lowest average monthly temperature and dividing by 2.

2.   April, May, and June is generally the driest time of year in Tucson.  This is reflected in the low montly average precipitation values.  It is fairly common to go a month or more without rain at this time of year.

      Because the air is dry and the skies are cloud free, there is generally a large difference between daytime high and nighttime low temperatures. 

3.   The summer thunderstorm season usually begins in early July.  The summer monsoon officially begins when the daily average dew point temperature is 54 F or above for three days in a row.  July, Aug, and Sept. are usually the wettest months of the year in Tucson.  Tucson gets nearly half its annual rainfall during the summer thunderstorm season. 

      Note how the difference between daytime high and nighttime low temperatures decreases once the summer thunderstorm season gets underway.  This is due to the increase in humidity and cloud cover.

4.   During the winter, middle latitude storms will occasionally drop far enough south to bring precipitation to southern Arizona.  Sometimes these storms will pull up moisture from the tropics and rainfall amounts can be significant.