The Curious Case of Long Standing High Temperature Records In the U.S.

Posted by

Average temperatures are rising across most of the globe and as the end of the year approaches, it doesn’t seem like it has been nearly as cold this year as it was in my childhood. Numbers from NOAA tend to back up that statement.

What is fairly interesting however is when you start looking at historical high and low temperatures by U.S. state, there are a couple of things that really stand out.

First (at least in my head) is the fact that Hawai’i and Alaska have the same record high temperature of 100 degrees F. Not terribly surprising for Alaska, which reaches its southernmost latitude at 51° North, but on the surface, very surprising for Hawai’i, which sits in the tropics at about 19° North at its closest point to the equator. 

The answer lies in the fact that many parts of Hawaii have a significant breeze and the ocean surrounding the state helps to keep things cooler in the summer than on the mainland. Very high temperatures usually don’t come about extremely quickly, instead needing a couple of days to be continuously warmed up by the sun (in mid-continent climates). Hot air doesn’t stick around very long in Hawai’i before it’s blown out to sea and replaced with 70-80 degree air coming in from the ocean.

Another statistical puzzle involves when many of these high temperature records were set. Only two states have seen state-wide high temperature records set since 1995: South Carolina (2012) and South Dakota (2006). In late June of 1994, 5 states saw record high temperatures within the span of 3 days. However, many records come from before 1960, with some standing for over 100 years.

Gathering scientific data is much more precise now than what it was back when some of these records were set. It may have been possible that a thermometer either sitting in direct sunlight, or catching the right amount of glare may have added a couple of degrees on an already extremely hot day. These days, standards are much higher when it comes to thermometer placement and we don’t rely on mercury anymore to let us know the temperature.