Because hotter air will hold more humidity than colder air which makes the relative humidity level lower when hot but when it starts to cool down the humidity goes up since cooler air can not hold as much moisture. That is why dew is on the ground in the mornings, when it cools down to or below the dew point that is.

 

For real moisture levels comparisons, convert temp/%RH to dew point or grains of moisture per lb of air.
75, 50% RH, Is a 55^F dew point. while 94^F, 50%RH is 73^F dew point, much more moisture.
The a/c mfgrs imply that you can control the indoor %RH with VS a/c. The fact is that your a/c's ability to remove moisture is dependent on the sensible cooling load and the actual amount of air flowing through the cooling coil. It is reasonable to expect 50%RH during significant sensible cooling loads, like the peak heat of the day. Evenings and cool wet days require supplemental dehumidification to remove excess moisture.
Get your tech to readjust the a/c to max the moisture removed while sensible cooling.
After you max the dehumidification of a/c, consider adding a small whole dehumidifier to your a/c for exact temp/%RH control. Units like the Ultra-Aire 70H added even a simple a/c will provide real %RH control even with the a/c off.
Keep us posted.
Regards Teddy Bear

 

Thank you DogBoy,

 

Thank you Teddy Bear,
for a detailed explanation of A/C dehumidification.
I have switch from merv13 to merv11 for a little better air flow.
My last Trane Thermostat didn’t register humidity, so I had no idea of %.
The Tech and the owner came out and made all the adjustments they could.
Unit does a nice job keeping it cold inside when it is 100 outside.
Thanks again, Vernon 31249