The register feels cold, so why is the house still warm
You put your hand up to the vent and the air coming out is genuinely cold, maybe even colder than you remember it being last summer. That's confusing, because the thermostat still says the house hasn't moved in two or three degrees after running most of the afternoon. In Nixa this complaint shows up a lot in July and August, when the humidity sitting over southwest Missouri makes the air feel heavier than the thermostat number suggests, and a system that's working at half capacity gets overwhelmed fast.
Cold air at the register tells you the compressor is running and making cold refrigerant. It does not tell you that cold air is actually making it into every room, or that enough of it is moving to keep up with the heat load on a 95 degree day with sun baking the roof since nine in the morning. Those are two different jobs, and a unit can do one without doing the other.
What local houses are dealing with
A lot of homes around Nixa and up toward Ozark were built in the 90s and 2000s during the growth years, with ductwork run through attics that get brutally hot in summer. Older farmhouses and homes closer to downtown Nixa sometimes have ducts that were added or modified over the years, with sections that were never sized right for the system now attached to them. Either way, duct condition matters as much as the equipment itself.
If your attic ductwork has gaps, disconnected sections, or insulation that's fallen away from the metal, you can be losing a real share of that cold air before it ever reaches the room. The register blows cold because the air leaving the unit is cold. What arrives at the far bedroom after traveling through a 140 degree attic is a different story.
More on this from Cold Air At The Register And A House That Will Not Drop.
What you can check yourself
Start with the filter. A clogged filter restricts airflow across the indoor coil, and when airflow drops too low the coil can start icing over even while the air at the register still feels cold for a while. Pull it and hold it up to a light. If you can't see light through it, replace it.
Walk the house and feel the output at every register, not just one or two. If certain rooms get weak, lukewarm air while others blow strong and cold, that's a duct or airflow balance problem, not a refrigerant problem, and it points toward attic ductwork rather than the unit itself.
Check the outdoor unit. Make sure nothing is blocking the sides, that the fan is spinning, and that there's no ice visible on the refrigerant lines running into the house. Ice on the lines on a hot day is not normal and means something is wrong with airflow or refrigerant charge.
Look at your thermostat settings and make sure it isn't set to a fan-only mode by accident, and that the batteries aren't low if it's an older unit. Simple, but it happens more than people expect.
Where this stops being a DIY job
If you've got strong cold air at some registers and weak or warm air at others, and the filter and outdoor unit both check out fine, that's a duct airflow issue that usually means sealing, insulating, or resizing ductwork in the attic. That's not a weekend project. Attic work in a Nixa summer is also genuinely dangerous heat exposure for anyone not used to it, so this is a point to call in someone who does it regularly.
Ice on the refrigerant lines or the indoor coil is also a stopping point. Running the system with a frozen coil can push liquid refrigerant back into the compressor and cause real damage, the kind that turns a simple fix into a full system replacement. Turn the system off, let it thaw completely, which can take several hours, and don't run it again until someone has looked at why it iced up in the first place.
If the outdoor unit is running constantly, never cycling off, and the house still isn't dropping even overnight when it's cooler outside, that points toward a refrigerant charge problem or a failing compressor. Both require gauges, training, and in the case of refrigerant, a license to handle it legally.
Why this matters more in late summer here
Southwest Missouri summers run hot and humid enough that an undersized or struggling system rarely catches up once it falls behind. A system that's been limping along since June, barely keeping pace on mild days, tends to fully give out during the stretch of 95 to 100 degree days that usually hits in late July or August. Catching the signs now, while it's still cooling some, costs less in every sense than waiting for the day it stops cooling at all.