First a brief tutorial on why we use dew point versus relative humidity:
It's more of an absolute measure which isn't relative to temperature. For example a relative humidity of 50% when the temperature is 95 degrees would feel incredibly tropical. An RH of 50% when the temperature is 55 degrees wouldn't feel nearly as humid. A dew point of 70 is super-tropical all the time. A dew point of 45 is comfortable regarding of temperature or time of year. This graphic illustrates this idea very well.
What's the most humid summer since 1950 in northern Ohio (Cleveland)? 1995
2018, 2010, 1987 and 1973 round out the top 5
I did some research on the years with the highest heat indices measured in hours in northern Ohio. You can read about it HERE (written in 2019)
There is an upward trend for more humid summers over the last few decades in northern Ohio.