‘Cool’ start to astronomical summer?

Heavy rain and storms have repeatedly made headlines across Northwest Missouri and Northeast Kansas over the past several months, seemingly leaving late spring and early summer heat by the wayside. In fact, the hottest day of 2026 thus far actually took place on March 21st, when St. Joseph set a new monthly record high of 95 degrees!

Fast forward to the first month of meteorological summer, a.k.a. June, 93 degrees is the hottest it’s been in St. Joseph in recent weeks. Most wouldn’t be complaining about a lack of 95+ degree heat this time of year, but some summer lovers may be annoyed by the string of 70s and low 80s that have been around for the second half of June. In addition to the lackluster heat, overnight lows have routinely fallen well into the 50s late in the season, keeping lake and pool temperatures a touch on the chilly side.

While meteorological summer started on June first, astronomical summer began with the estival solstice on June 21st. This is the longest day of the year in the northern hemisphere in terms of daylight hours, when the sun delivers the most radiant energy to this side of the equator. The driver behind all of this is the 23.5 degree tilt of Earth’s axis, the reason seasons exist as we orbit the sun throughout the year. 

In a cosmic joke of sorts, the high temperature in St. Joseph on the summer solstice last Sunday was only 71 degrees. That’s a full 15 degrees below the average high of 86 degrees on June 21st.

There are a few different reasons why the "official" start of summer was almost cool this year. Cloud coverage and rain-cooled air played a big role, combined with an almost brisk northeast wind that pulled a cooler air mass in from higher latitudes.

The bigger concept at play here is that of seasonal lag, a term for the delay in hottest or coldest temperatures on earth following the maximum or minimum in solar energy. Seasonal lag is the reason why summer heat is almost always more intense in July and August rather than June. It all boils down to the time it takes for solar energy to be transferred through earth’s vast oceans and into our atmosphere.

Those awaiting a summer sizzle need not worry, as early July is forecast to trend above average across a large swath of the U.S., including the Midwest and Great Plains.