Record Heat Coming

I used my last lime yesterday, but no way was I stepping foot outside to get more! That's a mission for a cooler tomorrow...

According to the climatologists, this pattern was a one in several thousand years event, and I still don't know if it won't happen again this summer.

PS:  Salem now has the same all-time high as Vegas.

A fun fact is that, while Portland was approximately 36 degrees above average on Sunday, the Continental United States, as a whole, was 1.4 degrees colder than average.   Portions of New Mexico, Colorado and Wyoming were almost 25 degrees below average.  The low in Laramie on Sunday was 39.

According to Jeff Berardelli, CBS' primary Meteorologist, the heat for all but the extreme Northeast and Northwest parts of Oregon was a 2.6-sigma event or below.  Portions of Alberta and British Columbia reached a 4-sigma event.

A 4-sigma event is a 1 in 15,787 event.  Some idiotic media types, who do not know what they are talking about, talk about a 1 in 10,000 year event, but it is not 1 in 15,787 years, it is 1 in 15,787 days.  That is still, though, approximately once-in-a-43 year event.

And this is where I get annoyed with media types, who do not know what they are talking about.  Because the 1 in 15,787 event refers to both four-sigma events above and below the 4-sigma range.  Thus, you would expect the high end of the range to only occur one in 31,574 times.  Thus, you would expect heat that deviates this far from the mean approximately once every 86 years, basically once-in-a-lifetime.  But that is just for Alberta and British Columbia.  

Where it gets tricky is that really, you can only expect to see highs like that in about 85 days out of the year.  Thus, you could argue that it would be more like a one-out-of-371 year event.  Still, under no circumstances a 1-out-of-10,000 year event.

To make it easy on me calculating, a 3-sigma event is a 1-in-369.5 day event.  As stated above, for high temperatures, you would expect for a 3-sigma high temperature to occur about once every 739 days.  In theory, you should expect a 3-sigma heat event once every nine or so years.  The fact that you do not in the summer seems to be because you typically do not see 36-degree deviations from usual highs in the summer.  You are much more likely to see 36+ degree deviations in Winter and Spring.  I have to believe that solar forcing is a part of that, because the Earth and Sun are closest together in January, because of the elliptical nature of Earth's orbit. 

You are much more likely, for example to see a rogue 90-degree day in Portland in March than a 112-degree day in June.

As for Las Vegas, the National Weather Service began keeping official records in Las Vegas on January 1, 1937.  The hottest ever was before 1937.  Las Vegas reached 118 degrees in July 1931 and may have been hotter before that.  But the National Weather Service wiped out all previous records in 1937.  The most recent hottest day in Las Vegas was on June 20, 2017.  But that is the fourth time that Las Vegas hit 117 since 1937.  

Yes, more than three standard deviations means that an event is outside of a 99.7% of all events (assuming normal distribution.)  In your example you are using two events a day. The high and the low temperature. But you ignored that in your example. So your reference is wrong or you are taking it out of context.