The short version
- El Nino winters in the Piedmont trend wetter and more erratic, which means ice storms and repeated freeze-thaw cycles rather than one long cold stretch.
- Moisture plus near-freezing air is the worst case for a heat pump, because the outdoor coil frosts over again and again and the system spends more time in defrost.
- Gas furnaces fail on the first hard call of the season, when a weak igniter, dirty flame sensor, or cracked heat exchanger finally shows itself.
- Test your heat now while a repair is a scheduled appointment instead of an after-hours emergency during an ice storm.
What El Nino actually means for Raleigh, Durham and Cary
El Nino describes warmer than average water in the central and eastern tropical Pacific. That shifts the subtropical jet stream, and for the Southeast the typical result is a wetter, stormier winter. NOAA's Climate Prediction Center has consistently tilted El Nino winters toward above-average precipitation across North Carolina.
Wetter does not automatically mean colder. It means the Triangle sits closer to the line where precipitation cannot decide what it wants to be. That is how we get the winters people remember here: 62 degrees on a Tuesday, freezing rain glazing the driveway Thursday morning, back to the 50s by the weekend.
For your heating system, those swings matter more than the low temperature itself. Equipment that starts, stops, and reverses constantly wears differently than equipment holding a steady load. Add the ice risk and the possibility of power interruptions, and the case for checking the system before the season is straightforward.
Heat pumps in freezing rain: what goes wrong
Most homes in the Triangle heat with a heat pump, and a heat pump does not create heat so much as move it. In winter it pulls warmth out of outdoor air through the outdoor coil. When outdoor air is both cold and damp, moisture condenses on that coil and freezes, and a frosted coil cannot absorb heat.
So the system runs a defrost cycle. It temporarily reverses, sends hot refrigerant outdoors to melt the ice, and usually energizes the backup heat so your house does not get a blast of cold air. That is normal and expected. What is not normal is defrosting constantly, staying iced after a cycle, or having the outdoor fan blades locked in a block of ice.
Warning signs worth a phone call:
- A solid sheet of ice covering the whole outdoor coil, or ice on top of the unit, that does not clear after a cycle.
- Auxiliary or emergency heat showing on the thermostat for hours in mild weather.
- The house holding 3 to 4 degrees below setpoint on a cold morning and never catching up.
- An electric bill that jumped far more than the weather explains.
- Water pooling and re-freezing under the unit, which points to a blocked defrost drain path.
Behind most of those symptoms is one of a short list of parts: a failed defrost board or sensor, a reversing valve that will not shift cleanly, a weak outdoor fan capacitor, low refrigerant charge, or restricted airflow indoors. All of them are testable. None of them announce themselves until you need heat.
Gas furnaces: the safety items we will not skip
A furnace that sat unused since March is being asked to fire reliably for the first time in months. The parts that fail first are predictable. Hot surface igniters crack. Flame sensors build up a film and shut the burner down seconds after lighting, which shows up as a system that starts then quits. Pressure switches trip on a blocked flue or a clogged condensate trap, and in a wet winter those traps matter more.
The item we will never sign off casually is the heat exchanger. A crack there can let combustion gases, including carbon monoxide, mix into the air moving through your house. That is an inspection with a light and a camera, not a guess. If we find one, we tell you plainly what it means and what your options are, including the ones that do not involve replacing the whole system.
If your home is on gas, also check that nothing is stored against the furnace, that the flue and intake are clear outside, and that every carbon monoxide alarm in the house passes its test button.
Your 5-point pre-winter checklist
All five of these are homeowner-safe and take under half an hour together. None require opening up equipment or touching wiring.
- 1
Run the heat for 15 minutes now, not in December
Turn the thermostat to heat and let it run a full cycle while it is still mild outside. Burning dust off a dormant furnace smells bad for a few minutes. What you are listening for is the system actually reaching temperature, the blower staying on, and no grinding, screeching, or repeated clicking.
- 2
Put in a fresh filter and write the date on it
A loaded filter starves airflow, and starved airflow is the single most common cause of a heat exchanger overheating or a heat pump icing up. A one inch filter needs changing every 30 to 60 days in winter. Media cabinets go 6 to 12 months.
- 3
Clear two feet around the outdoor unit
Heat pumps pull heat out of outdoor air all winter, so leaves, pine straw, and mulch packed against the coil directly cut your heat output. Rake it back, and never stack anything on top of the unit or run a cover over the coil.
- 4
Test every carbon monoxide alarm in the house
If you burn gas, propane, or oil, you need working CO alarms on every level and outside sleeping areas. Press the test button, and replace any alarm older than 7 years even if it still chirps.
- 5
Find your emergency heat setting before you need it
Know where the Em Heat or Aux Heat option is on your thermostat and what it looks like when it engages. If a hard freeze knocks your heat pump out at 11 PM, that switch is what keeps the house livable until a technician arrives.
Anything past this list means reading pressures, temperatures, and electrical values. Our free diagnostic guides will help you narrow down what is happening, and the DIY Playbook covers the repairs themselves. When it involves gas, refrigerant, or live high-voltage components, book a visit instead.
Why October beats January
In a cold snap, every heating company in the Triangle books out at once. The same repair that was a routine daytime appointment in the fall becomes a weekend or after-hours call, and after-hours work carries a $229 fee on top of the repair. Parts houses also run short on exactly the components everyone needs at once.
A pre-season tune-up is not a car wash for your furnace. We measure: amp draw on the motors, capacitor microfarads against the rated value, temperature rise across the coil or heat exchanger, static pressure, refrigerant performance in heating mode, defrost operation, safety controls, and combustion where it applies. Then you get the numbers and what they mean, not a vague thumbs up.
Our heating tune-up is $99 for the first system and $79 for each additional system, paid at the visit. We schedule 8 AM to 8 PM, seven days a week, across Raleigh, Durham, Cary, Apex, Wake Forest, and Chapel Hill.
Questions Triangle homeowners ask us every fall
Why does my heat pump blow cool air and steam outside in winter?
That is a defrost cycle and it is normal. When ice builds on the outdoor coil, the system briefly runs in reverse to melt it, so indoor air feels cool for a few minutes and the outdoor unit steams. It should last roughly 5 to 15 minutes and happen periodically, not constantly.
Is it bad if my auxiliary heat runs a lot?
Auxiliary heat is supposed to help during very cold weather or a large thermostat change. If it is running most of the day in 40 degree weather, something is wrong, and it is expensive. Electric heat strips can use three to five times the power of the heat pump doing the same job.
How cold does it have to get before my heat pump struggles?
Most older heat pumps in the Triangle start leaning on auxiliary heat somewhere in the 30s. Cold climate and variable speed systems hold their capacity much further down. The issue in an El Nino winter is not only how cold it gets, but how fast temperatures swing.
What is the point of a pre-winter tune-up if the system seems fine?
Most winter no-heat calls we run were measurable weeks earlier: a weak igniter, a capacitor drifting out of tolerance, a contactor pitting, a clogged condensate line. We test those values instead of guessing, so you find them in October instead of during a freeze.
What does a heating tune-up cost?
Our heating tune-up is $99 for the first system and $79 for each additional system, paid at the visit. Service runs 8 AM to 8 PM, seven days a week.
Get the heat checked before the first freeze
We will test the system, show you the readings, and tell you honestly whether it is ready for a rough winter. $99 first system, $79 each additional, paid at the visit.