We are up in the Nth East. I assume coastal areas maybe even worse. The temps have dropped here to around 35 degrees but humidity between 70-80%. Our Samsung AC's are nothing special (non inverter), about 7 years old and serviced every 4-6 months. All are the right size for the rooms and normally work well with Thermostat set on 27-29 degrees. This time of year in the wet season for at least a month or two they seem to be just barely coping. Had it set on 23 tonight and is a lot cooler than outside but not what I would call a comfortable room temp.

 

Anyone else experience the same thing? I reckon working about 50-60% of there normal efficiency

I normally run my A/C's at 27 C.

 

Perhaps it might be worth checking refrigerant level. That's usually the cause of poor functioning, low levels.