Triple Digit Heat?

There has been a lot of talk about hitting 100 today or tomorrow.  As I type this, the National Weather Service Forecast National Blend of Models, which forecasts a distribution of max temperatures based on forecasts from many modeling systems, is producing a median forecast of 99°F for the airport today.  The middle 50% of forecasts, also known and the interquartile range, is between 98°F and 100°F.  

Source: https://hwp-viz.gsd.esrl.noaa.gov/wave1d/?location=KSLC

One way to interpret that is that it is more likely than not we'll be at 99 or a bit lower, but the odds of 100 or a bit higher are roughly 25% (I'd need access to higher precision data to provide a more detailed estimate).

Tomorrow, the numbers edge up slightly, with 100°F being the median forecast, so we'll call it 50/50 for tomorrow. 

Source: https://hwp-viz.gsd.esrl.noaa.gov/wave1d/?location=KSLC

Is this unusual?  Yes.  Since record keeping began in 1874, there have been 10 days with a high temperature of 100 or more on or prior to June 13.  This is based on observations taken in downtown Salt Lake City until about 1928 when the site was moved to the airport.  

The table above lists the 40 hottest days on record prior to June 13. One can see the impacts of a few early June heat waves, the earliest being in 1918, which has 3 of those days.  26 of the days have been since 2000.  

Please note that the National Weather Service has issued a heat advisory for much of the Wasatch Front and West Desert due to the high temperatures.  

Summer heat is sadly here.  There is some hope that tomorrow will be the worst of it (see plots above).  Let's hope that's the case.