That first cold morning smell and noise
You turned the thermostat down to heat sometime in October, more out of habit than need, and the furnace clicked on without complaint. Then the real cold showed up, the kind that rolls through southwest Missouri in a hard front off the plains, and suddenly the furnace is doing something it wasn't doing before. A burning dust smell that won't quit after twenty minutes. A rattle on startup. Or nothing at all, just cold air coming out of the vents while the thermostat insists it's working.
This is not bad luck and it's not a coincidence that it happens on the coldest night. A furnace that sat idle since March and is asked, without warning, to run for eight or ten hours straight is going to expose every weakness it was hiding all summer.
Why Republic homes see this pattern
Republic and the rest of the Ozark border country get long, mild falls that lull people into leaving the furnace alone, then a sudden air mass swings down and drops temperatures thirty degrees in a day. That first real cold snap is usually the first time the system has run continuously since the previous winter. Anything that degraded quietly over the summer, a cracked heat exchanger seam, a weak capacitor, a dirty flame sensor, gets discovered under load rather than during a gentle test cycle.
A lot of the housing stock here is a mix: older farmhouses and ranch homes from the 60s through 80s with original or once-replaced ductwork, and newer builds out toward the edges of town on slab foundations with tighter, more complex systems. Both have their own failure points. Older homes often have furnaces installed in crawlspaces or unconditioned garages, where summer humidity and rodent activity do slow damage to wiring and gas lines that nobody sees until the unit is asked to work hard.
More on this from furnace repair in Republic.
What you can check before calling anyone
Start with the filter. A filter that's been in since spring is choked with a summer's worth of dust and mowing season debris, and a restricted filter is the single most common reason a furnace overheats and shuts itself off on the first cold night. Pull it, hold it up to a light, and if you can't see through it, replace it.
Check the thermostat batteries if it's a battery model, and make sure it's actually set to heat and not just a lower cooling setpoint left over from summer. Walk around and listen for the furnace attempting to start, a series of clicks followed by silence usually means the igniter or flame sensor is failing, not something you can fix with a screwdriver but useful information to give whoever comes out.
If you have a crawlspace or basement furnace, look at it with a flashlight for anything obviously wrong: scorch marks, a rusted-through flue pipe, or a nest of insulation somewhere it shouldn't be. Don't take the cabinet apart. Just look.
Where it stops being a homeowner job
Gas smell, any gas smell, means you shut the system off, don't flip switches or light anything, and get out. That's not a furnace repair situation, that's a call-someone-now situation.
Anything involving the heat exchanger, the gas valve, the control board, or repeated ignition failures needs a technician with a combustion analyzer and the training to test for carbon monoxide leakage. A cracked heat exchanger in particular is invisible to a homeowner and dangerous enough that it's the main reason furnace inspections exist at all. If your furnace is running but you're getting inconsistent heat, short cycling, or that burning smell that doesn't fade, that's your line. Stop troubleshooting and get it looked at.
Getting ahead of the next cold snap
The honest fix for this pattern is not waiting for the first hard freeze to find out what broke over the summer. A furnace that gets a look in September or early October, before the first real cold front, gets its problems found on a mild afternoon instead of a fifteen-degree night. In this part of Missouri that window is short but it's real, usually a few weeks between the last warm stretch and the first cold snap.
If your furnace is original to a house built before the 90s, or it's given you trouble the last two winters in a row, that's worth taking seriously rather than hoping this year is different. Furnaces don't fail because of one bad night. They fail because a small problem sat there all summer waiting for a night cold enough to find it.