Wednesday, August 1, 2018

July in the Rear View Mirror, Thankfully

A little something to get you going on this August 1st as we put July in the rear view mirror and begin to look forward to cooler times.

The weather this July can best be described using words like ugly and heinous.  

At the Salt Lake City International Airport, the mean temperature for the month was 83.1˚F, tied for 5th warmest all time.  
Source: NOAA Regional Climate Centers
And here's a factoid for you.  The 11 warmest Julys have all happened in the 21st century.  People in Salt Lake simply didn't suffer like this in the 20th century.  If you go back to Y2K, the hottest July on record was 81.2˚F (1960).  Now, it is 85.3˚F (2017). 

Source: NOAA Regional Climate Centers
Digging in beyond the mean monthly temperature, the mean maximum and mean minimum for the month were 95.5˚F and 70.7˚F, respectively.  The former only rates as the 14th warmest on record, but the latter is the 3rd warmest.  Minimum temperatures are a big driver of comfort as they allow for cooling of the home and good overnight sleeping weather.  Sadly, this July saw a very high mean minimum temperature, 21 days with a minimum temperature 70˚F or higher, and a run of 13 consecutive days (5-17 July) above that threshold.

It is interesting to compare July 2018 to the hottest July in the 20th century, 1960.  1960 featured a mean temperature of 81.2˚F, 0.9˚F cooler than this July, but the average daily temperature range was much larger with maximum and minimum temperatures of 98.2˚F and 64.2˚F, respectively.  I suspect 1960 would have been far more comfortable as a whole due to the lower minimum temperatures.  

How about precipitation?  It was scant.  The total for the month was 0.19 inches.  That rates as the 34th driest out of 145 years, so not exceptionally dry, but dry nonetheless.  If you are wondering, there have been four Julys with only a trace, so it is possible to get "shut out" or at least nearly shut out.

For the summer to date (i.e., 1 June - 31 July), we've had 0.24" of precipitation, which rates as the 11th driest.  I've noticed that virtually nothing is growing in my gardens and I've mowed my grass about once in the past 6 weeks.  I try to water at what I consider to be a minimum plant survival level and little rain and the heat, it appears I'm right on that level. 

July is the month with the smallest amount of year-to-year variability in temperature in Salt Lake City.  If one looks at the chart above and does an eyaball, there's about a 5˚F range in mean temperature for the month, with a few outliers.  One of those is 1993 when the mean temperature was 69.9˚F (and the mean minimum temperature was and incredible 56.1˚F).  I have a dream that July 2019 is the new July 1993. 


  1. I've been wondering. At what point does urban heat island effect mixed in with the Salt Lake Valley's growth (especially with the new prison and inland port), start making Salt Lake airport temperatures unreliable comparisons to the past? When do we start transitioning to using something like temperatures out far away, like on Antelope Island?

  2. I think there is little doubt that urbanization is affecting measurements at the airport. I do not see that as a problem.

    There is no site anywhere near hear that is "representative". The terrain and development contrasts mean that there are lots of variations in local climate. We need to understand it all. The airport is just one point.

    Really, the most important thing is to have many observations that broadly encapsulate what is going on around the area, which is one of the reasons why mesowest integrates observations from all sorts of networks.


  3. I like the PJ reference! Great band and they are extremely environmentally conscious. They strive for zero net emissions on their tours and Eddie Vedder is quite active in causes that seek to protect our oceans. I know this has nothing to do with the blog's subject, but I got excited when I saw the reference.