Monthly Archives: August 2014

Tucson Weather – More History In Charts (8/26/2014)

I got some positive responses from the last post on monsoons in Tucson, so I decided to stay with the weather theme for one more late summer boondoggle. This time I reviewed trend in local temperature. The charts come straight from NOAA/National Weather Service website and I a present them as they are with limited personal comments.

Exhibit 1 shows average yearly temperatures along with “normals” and 10 year moving averages. There has been a sustained increase in average temperatures since 1970s (panel 1). Interestingly though, high temps increased only slightly and majority of the trend can be accounted for by fast warming of the daily lows (panel 3). Undoubtedly, this must be related to the “urban heat island” phenomenon. More information of UHI can be found in this local report. The timing makes sense as Tucson was rapidly urbanized around then with population growing by astonishing 368% in the 1960’s (Exhibit 2).

Exhibit 1 – Average Temperatures


Source: NOAA/National Weather Service, Tucson Arizona

Exhibit 2 – Tucson Population Growth by Decade


Source: Wikipedia

Another trend I found interesting is the data on occurrences of 100+ degree days (Exhibit 2). This unpleasant (for most of us?) side-effect of living in the desert became more pronounced lately. In the past ten years we averaged about 65 such days a year, up from 50 or so a century ago. It’s not all bad though, as there has been a corresponding decrease in days below freezing point (panel 2). Personally, I could do with even fewer frost days so I don’t have to cover all my plants with sheets and blankets!

Exhibit 3 – Occurrences of Extreme High and Low Temperatures


Source: NOAA/National Weather Service, Tucson Arizona


This was just a quick post highlighting local climate trends I personally found interesting. There is a plethora of very cool and interesting Tucson climate data available on the NOAA website.

You can see a pdf with annual data including full set of charts and record tables here:

Or even more detailed data by month, season, etc here (click on season link for pdf):

Tucson Monsoon – A History In Charts (8/4/2014)

Warning: this post is a bit of mid-summer boondoggle and contains no financial planning wisdom whatsoever.

The monsoon season in Arizona is in full swing and I decided to take a look at how current patterns compare to the historical rainfall. Around here you always hear about how monsoons aren’t as good as they used to be, so let’s see what the data tells us.

Exhibit 1 shows annual monsoon rainfall (June through September) in Tucson for the past 120 years. There doesn’t seem to by any apparent pattern, it ebbs and flows with wet and dry years interspersed throughout the century. The dotted red line is the trendline for the period and it actually has a slightly positive slope, which means the average precipitation amount has increased over the years.

Exhibit 1Annual Monsoon Rainfall In Tucson (Inches)


Here is the same data broken down by decade (Exhibit 2). Once again, the amount of rainfall has stayed remarkably consistent. Sure, 2000’s were a bit dry but so we few other decades with 1970’s coming in lowest.

Exhibit 2


Ten wettest and driest monsoon years are shown in Exhibit 3. Since 2000, we have seen two of the highest rainfall years and two of the lowest.

Exhibit 3


Just in case you were wondering, Tucson has the highest average monsoon levels among the major Southwest cities (Exhibit 4). Our friends in Phoenix get less than half of our rainfall.

Exhibit 4



They data I analyzed does not support claims of the declining monsoon rainfall in Tucson. If anything, there is a slight uptrend over the last century plus.

Data Sources

You can find these data and much more on the National Weather Service website:

 Here is the explanations of the monsoon mechanics: