Not All Daily Temperature Records Are the Same

Yesterday, the temperature at SeaTac Airport rose to 89F,  beating the all-time daily record for the date (86F)!

Today, even if the temperature is the same, it won't break any records.

How could this be?

It turns out that not all records are equal.

Let me explain.

Below is a plot of observed temperatures (blue bars), average temperature range (brown band),  and record highs (red) and lows (blue) for June at Boeing Field in Seattle.

Look carefully at the record highs.   A large variation of record highs in June from 81F to 104F!  Generally around 90F.   

So why the variability?    

It turns out that to get the really high temperatures in western Washington, the atmosphere needs to organize itself in a very specific way, generally with a strong upper-level ridge and offshore-directed flow at low levels.

And on some days, by the luck of the draw, the atmosphere gets the right setup for maximal heat. After many years, the needed flow pattern occurs, and the temperature climbs to record levels.

Global warming plays very little role in these records---the key is getting the right atmospheric flow situation.

Would you like me to prove this to you?

Here is a plot of the highest maximum temperature each year between June 7 and June 21 since 1950 at Olympic Airport (a less urbanized location than SeaTac).   No apparent upward trend.

Turning back to SeaTac, below is a plot of the highest temperature on June 14th at that location (below).  

2025 was the warmest year on record for that date.  But note!  There is no trend in the record temperatures for that date over the entire period of record.

In fact, the highest temperatures on June 14th are trending down!  (brown line).  

So the global warming claims for the origin of such records should be taken with a large grain of salt.