September is West Virginia’s quietest month, with heating and cooling demand together adding up to about 189 degree days. That’s a real number, not a guess, and it sits closer to the high end of what any state’s calmest month looks like nationally. The mechanics behind that figure, and what it actually means for the thermostat on your wall, are worth walking through before you touch a single switch.
The quietest month in West Virginia
Degree days measure demand, not temperature. Each one represents how far the average daily temperature strayed from 65°F, the point where a house typically needs neither heating nor cooling. A day that’s 75°F outside logs 10 cooling degree days; a day at 45°F logs 20 heating degree days. Add every day’s tally across a month, and you get a single number that tells you how hard the house had to work, not how hot or cold it felt on any given afternoon.
Across the fifty states, the calmest month anywhere runs about 70 combined degree days on the low end, and as high as 246 on the high end. West Virginia’s September, at 189, lands well up in that range, closer to the busy side than the quiet one. That’s the honest answer to the question this page is built to answer: there is no month here when the house asks for nothing.
What September actually feels like, described without inventing numbers that aren’t in the record, is a month where the cold has mostly let go but the summer humidity hasn’t. Mornings can still call for a jacket, afternoons still push air conditioners into service, and the two demands overlap enough that neither system gets a clean, extended rest. Add to that the fact that the reference station in Charleston averages 16 days a year at 90°F or hotter, most of them landing in the months just before September, and you get a summer that eases rather than ends. The quietest month in West Virginia is real. A true pause is not.
Shutting the heat down for the year
The changeover away from heat isn’t a single flip of a switch. Done in order, it protects the equipment and sets up a smoother restart in the fall.
- Turn the thermostat off the “heat” call first, rather than cutting power at the breaker or switch, so the system stops on its own terms.
- Let the system finish its current cycle, including the blower running down, before you do anything else at the unit.
- For gas- or oil-fired furnaces and boilers, leave the fuel supply and pilot or ignition system exactly as the manufacturer’s guidance directs. This isn’t a step to improvise.
- Inspect, clean, or change the filter now, on the changeover itself. ENERGY STAR’s own maintenance guidance is blunt about the schedule: “Inspect, clean, or change air filters once a month in your central air conditioner, furnace, and/or heat pump.” That’s every system with ductwork, not furnaces alone, and once a month, not once a season.
- Shut down any humidifier mounted on the ductwork. It’s the step almost everyone forgets, and running it dry all summer does it no favors.
- Finish with the physical tidy-up: clear registers and return vents, wipe down the area around the furnace or boiler, and note where any bypass damper is set so it’s easy to reverse in the fall.
One caution matters here more than in warmer states. With heating demand running from October through May and a heating load that never fully disappears until June, West Virginia isn’t a place where the system can be shut off completely for an extended stretch without risk. Homes with exposed plumbing, especially in higher elevations, should keep a backup heat source or a minimum setpoint active rather than killing the system entirely.
The first run of the cooling season
The best day to test the air conditioner is a mild one, well before the first real heat wave. A fault caught on a 75°F afternoon is an inconvenience; the same fault discovered on the first 90°F day of the year is an emergency.
- Clear leaves, mulch, and debris from around the outdoor condenser, giving it at least a couple of feet of open space on every side.
- Check the condensate drain line for clogs or standing water, since a blocked line is the most common cause of an early-season shutdown.
- Change or wash the filter, whether or not it looks dirty. A season sitting idle is enough to matter.
- Run the system in COOL for a full cycle on that mild day, letting it reach the setpoint and shut off on its own.
- Feel the air coming out of a register far from the unit, not the closest one, to catch weak airflow before it becomes a comfort complaint in July.
ENERGY STAR puts a number on why that filter step matters so much: “Airflow problems can reduce your system’s efficiency by up to 15 percent.” A system can be mechanically sound and still underperform badly on a dirty filter alone.
What this checklist looks like in practice depends on what’s actually installed. In West Virginia, 89 percent of homes run some form of air conditioning, but only 64 percent run a central system. The remaining 25 percentage points are running window units, portables, or ductless mini-splits, roughly a third of all homes statewide. Those households skip the condensate-line and ductwork checks and instead need to confirm the unit still seats tightly in the window or wall opening after a winter of vibration and weather. Ceiling fans, found in 82 percent of homes here, are worth turning on with the first cooling run too. They let a system hold a slightly higher setpoint without anyone noticing the difference.
The days that ask for both
Every homeowner in this state recognizes the week where the furnace kicks on before sunrise and the air conditioner kicks on by mid-afternoon. It isn’t a malfunction. It’s the calendar catching up with a house that has two different jobs to do in the same 24 hours.
Using the monthly figures for this station, one month stands out where both loads are genuinely present: May, with 104 heating degree days and 94 cooling degree days. That split comes from a threshold stated here for clarity, at least 50 of each in the same month, not a category NOAA itself publishes. April comes close on the heating side but its cooling load is too thin, and June flips the other way. May is the one month where the house is genuinely doing both jobs.
| Approach | What it does | Tradeoff | When to use it |
|---|---|---|---|
| AUTO changeover mode | Thermostat switches between heat and cool automatically as the temperature crosses each setpoint | Convenient, but a narrow gap between setpoints can trigger both systems in the same day | Homes wanting hands-off comfort through a transitional month |
| Wide deadband between setpoints | Leaves several degrees of “do nothing” room between the heat setpoint and the cool setpoint | Costs nothing and prevents the system from reheating air it just cooled, or the reverse | Any home in AUTO mode during May |
| Manual mode, heat only in early morning | Lets the house drift warmer on its own through the afternoon | Requires a manual switch-back if the evening turns cold again | Mild days with a clear evening cool-down expected |
| Open windows instead of running either system | Uses outside air directly rather than mechanical heating or cooling | Free, but only works when outdoor humidity and pollen are tolerable | Mild, dry stretches within May |
The expensive mistake is a deadband set too narrow, sometimes just a degree or two. That gap lets the furnace warm the house in the morning, then hands that same air straight to the air conditioner by afternoon, paying twice for a comfort swing the house would have handled on its own with a few more degrees of slack.
And the changeover in the other direction
Heating demand starts building again in October, the first month where the average temperature at the Charleston reference station drops back below the 65°F line NOAA uses to count heating degree days. It climbs fast from there, peaking in January, and doesn’t fully let go again until June, an eight-month season that leaves little slack on either end.
What that fall checklist should focus on depends on what’s actually installed. Furnaces are the dominant heating equipment here, found in 54 percent of homes, with central heat pumps in another 20 percent. Boiler, oil, and propane shares weren’t published in reliable enough numbers to report for this state, which means suppressed, not absent, and any home running radiators off a boiler should follow boiler-specific guidance rather than a furnace checklist. Heat pump owners have one extra step furnace owners don’t: confirming the defrost and reversing-valve cycle runs cleanly before the first cold snap arrives. The full pre-season list, ignition checks, thermostat programming, and the rest, belongs in a dedicated heating-season guide rather than repeated here.