Why Has Spring Been So Wet/Cool?

The overall pattern this spring has lacked substantial warm periods. Yes we've reach 80 degrees a few times earlier in May but nothing since. Add the high frequency of rainfall and this spring has been anything but pleasant. It's not only across northern Ohio but a large portion of the Great Lakes, Ohio Valley and central US.

Below are the temperatures compared to normal over different time periods since early April. Shades of blue represent below normal temperatures. Notice that most of the extremely "cool" air occurred in the last 2 weeks of May.

May 23 to May 30

May 15 to May 30

May 1 to May 30

April 1 to May 30

The percentage of days with high temperatures above normal is low since April 1st.  One of the biggest drops year to year. April/May of 2024 featured 74% of the days above normal.  This year only 36%.  We forget that 2020 we only had 28% of the days above normal

Rainfall vs normal across the US over different time intervals:

May 23 to May 30

May 15 to May 30

May 1 to May 30

April 1 to May 30

Interestingly, the Ohio Valley has had well above normal rainfall from Ohio, western PA south along the Ohio River including the entire deep south. Yet northern Indiana, Illinois and all of Iowa is running 2-5" below normal since early April.

Here is a close up look at Ohio's rainfall since early May:

Why has this spring featured above normal rainfall and a high number of days with below normal temperatures?  The answer is multi-faceted. First, the weak La Nina continues to weaken in the tropical Pacific. Second, the upper atmosphere over the North Pole went through a warming in mid March. (stratospheric warming). This resulted in the Polar Jet stream to buckle south resulting in periods of unsettled weather across the middle of the US and southern Canada this spring. It's been a slow developing process over the last 2 months. (If this "warming" would have occurred in January, the chances would have been much higher that this winter would have featured more extreme cold!)

The stratospheric warming is identifiable by looking at the high pressure over the North Pole. Notice that it descends down into the middle of the atmosphere. It tool a long time to "drip" deeper into the atmosphere after the initial warming in mid March.  (graphics below courtesy Judah Cohen)

The trickle-down continued well into May.  

Another way to look at this is to chart the temperature increase. The area in black shows the rapid rise to almost record levels at the top of the atmosphere in mid March.

The rise was accompanied by a reversal in the upper level winds. The red line which dropped below the blue dashed line shows this perfectly.  This reversal weakens the polar vortex which allows more frequent periods of "cooler" air and an active storm track.

The upper level pattern in April shows the storm track across northern Canada, a ridge of high pressure across the eastern US/New England and the low developing in the SW US.

By May, the SW low deepened and became a permanent fixture across the central US, Ohio Valley.  This matches up with the cooler temperatures in the graphic at the top of the post.

Here's a close up image of the upper level pattern in May

Remember that the cooler and unsettled influences are kind of like tentacles off an octopus. They extend and retreat. When they retreat, you get periods of warmth, which we've had similar to late last week when we reached the lower 80s. When they extend you get periods of rain/highs in the 50s and 60s when the average highs are above 70.

We've had more than 30 days with measurable rainfall since April 1.

8th wettest April and May thus far.

Number of days with measurable rainfall - April 1 thru May 31:

1953                 41

1973                 39

1947                 38

2011/2002         37

1989-05-31         36

1956/1943         35

2025/2019/2004 34

Cloud cover has been well above normal this month.  When we look at the April/May cloud cover vs normal for each year over the last decade we notice several things.  May 2025 is the cloudiest May since 2020 with April cloud cover is only slightly above normal.  The biggest takeaway item about this chart is the April-to-May cloud cover increase vs normal is more than any year in over a decade!

This pattern extends to most of the mid-west, Great Lakes and New England. This has also influenced the multiple severe weather events.  Luckily the Ohio tornado count way down from last year.

How Common Are Spring Temperature Swings In Northern Ohio?

Our human nature is an exercise in self-deception. In the case of weather, our biases can undermine how we look at weather forecasts and past weather events. I like to call it "Behavioral Meteorology". Here's is an example that I guarantee has been said thousands of times over the last several days: "This Ohio weather is crazy! I don't remember changes like this. Wait five minutes and it'll change."

Just look at the high temperatures over the last 2 weeks. 46° to 28°.   40° to 63°.  33° to 52°. Plenty of ups and downs. It's easy to draw the conclusion that these big changes are unusual. 

Look at the temperature forecast through St. Patrick's Day across the eastern US.

But when we look at the entire middle of the country, the locations that see the greatest frequency of day-to-day temperature change might surprise you. The central US -- Eastern Nebraska, northeastern Kansas, northwestern Missouri, portions of Iowa and southern South Dakota -- experience the largest day-to-day temperature swings especially in March and April. Ohio is on the list but no where near the top.

How did I figure this out? I downloaded the high temperatures for each day for 20 cities over the last 50 years. I found the day-to-day high temperature differences and counted up the instances when it was more than 20 degrees. I plotted the results on the map above. For northern Ohio, I tabulated the totals for each month and graphed them below.

This year was the coldest in northern Ohio in a decade (winter of 2014-15). The number of days with high temperatures under 30 was the highest in 7 years. We had triple the number of days with snow on the ground compared to last winter. Large high temperature changes this winter only happened 4 times of at least 15 degrees.

Snow and cold in December through February has been replaced with rain and milder air. These warmer changes are welcomed. But subconsciously, they make us feel uneasy as we try to make sense of rapid temperature changes historically.  Psychologists call this "Cognitive Dissonance". None of us like to feel uncertain or conflicted.  We all have a built in motivation to reduce conflicting ideas by altering the existing conditions in our mind to create consistency. How many times recently have you had a conversation with someone and they said, “What is the deal with this crazy weather…what is going on here?”

Our weather perceptions are powerful.

Here a chart showing the March-April-May instances since 1950 where the high temperatures change more than 20 degrees day-to-day. The average is between 4 and 6 each spring. No big changes over the years in northern Ohio.

We view the weather through our own senses. We interpret all of this information through our own individual frame work. This frame work is built through our own experiences coupled with a hard-wired lens that shapes what/how we view what occurs around us.  We are inclined to favor information that reinforces our comfort level and preconceived notions. This is called a "Confirmation Bias". The problem is that by creating "consistency" through favoring information, we can create a new false interpretation of the weather which we believe to be true. In a nutshell, our own human nature deceives us. Our biases "cloud"--no pun intended--our judgment of the weather changes.

As much as we perceive these fluctuations to be a new thing here in northern Ohio, it is quiet common in early spring. Will these big changes continue in the weeks ahead?  Just look at the temperatures over the next 2 weeks!