Fall Camping in the Rockies: The Gold Weeks Are the First Sub-Zero Weeks — and What That Costs in Propane

The weeks the larches go gold are the weeks the overnight lows go under zero. Those are not two seasons that happen to overlap. They are the same three or four weeks, and in the Rockies that means anyone planning a fall camping trip for the scenery is planning a cold-weather camping trip whether they meant to or not.

Most people work that out at about 2 a.m. on the first night.

The question that follows is always the same, and we get it in the booking thread every September: how much propane does that actually take, and will we run out. Nobody answers it with a number. We have written the phrase “you’ll go through more of it” into half a dozen posts on this site without once saying how much more, so here is the arithmetic, including the part that surprises people — a bottle can stop delivering heat while there is still propane sitting in it.

How cold does it get in Banff in September and October?

Parks Canada’s own numbers for the Banff townsite: September averages a daily high of 16.1 °C and an overnight low of 2.7 °C. October averages 10.1 °C and −1.1 °C. November averages 0.5 °C and −8.2 °C.

Read the October line again, because it is the one that decides your trip. That −1.1 °C is the average overnight low, not the cold snap. Half of October’s nights are colder than that. Banff also picks up an average of 7.0 cm of snow in September and 18.9 cm in October — not enough to change your driving plans most years, and more than enough to change your sleeping plans.

Then there is elevation. Parks Canada puts the drop at roughly 1 °C for every 200 m you climb, and almost every campground you would want in larch season sits above the townsite. Take that as a floor rather than a forecast: cold air pools in these valleys overnight, and the gap can run much wider than the lapse rate predicts. Parks Canada’s own figures show Lake Louise — only 130 m higher than Banff — averaging a November low of −13.9 °C against Banff’s −8.2 °C. That is a 5.7 °C spread that elevation alone does not explain.

So the planning number for a late-September or October trip is not “around freezing.” It is “below freezing most nights, colder than the townsite, and occasionally a lot colder.”

Is it worth camping in Banff in October?

Yes, and the reason is the one thing a day trip cannot buy you: you are already there at first light. The larch slopes, the golden aspen along the Bow, the first snow sitting on the peaks above bare gold — all of it looks completely different at 7 a.m. than it does at 11 a.m., and at 11 a.m. you are sharing it with everyone who left Calgary at eight.

Frost on the meadow, mist coming off the water, elk bugling somewhere you cannot see. You get about ninety minutes of that before the first day-trippers arrive, and you only get it if you slept out there.

The scenery itself is well covered elsewhere on this site — where the paved larch drives are in Kananaskis, and how to see larches in Banff without the Moraine Lake shuttle. What those posts do not tell you is what it takes to be standing there at dawn in the first week of October, which is a trailer with a furnace and enough fuel to run it.

It is also why this is a Yetti trip and not a KZ Connect trip. The KZ is the better trailer for a big group in August — it sleeps up to ten and it has the outdoor kitchen — but it is a three-season unit with an open underbelly and exposed tanks, and we have written about exactly how late you can push it. October in the Rockies is past that line. The Yetti has an enclosed insulated underbelly with an Arctic package rated to −30 °C and a furnace ducted into the underbelly and the holding-tank compartment, which is the difference between waking up cold and waking up with no water system.

How much propane is in a 20 lb bottle?

About 431,000 BTU. The Propane Education and Research Council’s technical guide puts propane’s heating value at 21,548 Btu per pound, so a full 20 lb bottle carries roughly 20 × 21,548 BTU. Two full bottles, which is what a trailer like ours carries, is about 862,000 BTU of heat to spend.

One clarification worth making, because it is the most common mistake in every propane explainer online. Propane bottles are filled to 80 per cent of their volume so the liquid has room to expand, and new bottles have an overfill prevention device that enforces it. True — but the “20 lb” on the bottle already is that 80 per cent. It refers to 20 lb of propane in a bottle whose shell could physically hold more. So you do not discount the 20 lb by another 80 per cent. Plenty of people do, and end up planning their trip around a number roughly 20 per cent too low.

How long does a propane bottle last in an RV furnace?

Divide the bottle by the furnace. An RV furnace of the size fitted to a trailer in this class has an input rating somewhere around 20,000 to 30,000 BTU per hour — the exact figure is on the label on the furnace body. At 25,000 BTU/hr, a full 20 lb bottle gives you about 17 hours of continuous burn.

Furnaces do not burn continuously, which is where the calendar time comes from. The furnace fires until the thermostat is satisfied, shuts off, and waits. The fraction of the hour it spends actually burning is the duty cycle, and that is what the outside temperature moves:

• On a mild night just below freezing in a well-insulated four-season trailer, call it a quarter to a third of the time. Those 17 hours stretch to roughly two to three days.
• On a genuinely cold night, closer to half. Call it a day and a half.
• Add the fridge running on gas and the water heater, and take something off the top of both figures.

So the honest planning answer for two full bottles in October is three to five days, and in a hard cold snap rather less. That is arithmetic with stated assumptions, not a measurement — run it again with your own furnace’s label rating and your own thermostat setting and you will get a better number than any blog can give you.

The useful part is not the answer. It is that you can now tell the difference between a trip that comfortably fits its fuel and one that does not, before you leave Calgary.

Why does the RV furnace quit when there’s still propane in the tank?

Because propane has to boil out of the liquid before the furnace can burn it, and cold slows that down. The PERC technical guide states it plainly: “when the outside air temperature is lower or the container has less liquid in it, the vaporization rate of the container is a lower value.”

Both halves of that sentence are working against you on an October night. It is cold, so vaporization is already slow. And as the bottle empties, the liquid’s contact area with the bottle wall shrinks, so it gets slower still. Push hard enough — a furnace running long cycles in real cold off a bottle that is nearly done — and the furnace draws gas faster than the bottle can make it.

What that looks like at 3 a.m. is not an empty tank. It is a furnace that runs, falters, and stops. Wait fifteen minutes and it will run again for a while, then stop again. It reads as a broken furnace, and people spend a freezing night troubleshooting an appliance that is working perfectly.

This inverts the advice everyone gives. “Make sure you don’t run out of propane” is not the rule. The rule is change bottles before they get low, not when they run dry, because a half-full bottle in the cold outperforms a nearly-empty one. Run the first bottle down to roughly a third, switch to the full one, and refill the first at the next opportunity. You are managing vaporization rate, not fuel quantity.

If your trailer has an automatic changeover regulator, it does this for you — but only if the second bottle is actually full, which is the part people skip.

Does a powered campsite change the propane math?

Completely. On a site with a 30-amp hookup, propane stops being the thing you ration. Our standing advice to guests has not changed: fire the propane furnace when you arrive and let it bring the enclosed underbelly up to temperature, because propane moves heat fast and it is ducted where the plumbing is. Then hold the night on electric. Propane does the heavy lifting, hydro does the maintenance, and you are not burning a bottle to get through one cold night.

On an unserviced site it is propane from dusk to dawn, and the numbers above are the ones that apply. Which campgrounds still have power in October is its own question, and we have answered it for Banff and for Kananaskis separately — worth reading before you book, because the electrical loops fill first in the fall for exactly this reason.

What we send you out with

Both bottles full. That is not a courtesy, it is the whole plan — the vaporization problem above is much easier to avoid than to fix at 3 a.m. in a campground with no cell signal.

If you do not have a truck that can tow it, that is the normal case rather than the exception, and it is what the delivery service is for. The Yetti is 5,875 lb dry and closer to 6,800 lb loaded, which rules out every SUV people ask us about — and no, renting one of our Sierras is not the workaround, because Turo’s terms prohibit towing with a rented vehicle. We tow the trailer to your site, level it, connect the propane and battery, and walk you through the furnace and the changeover regulator before we leave. At the end of the trip we come back and take it away.

Delivery range, fees and availability live on the RVezy listing and change with the season, so check there rather than taking a number from a blog post. Late-season delivery into the parks is also weather-dependent — we will tell you straight if the forecast makes it a bad idea.

Book the Yetti for larch season

The gold is here now and it does not wait. Two-day minimum on every booking.

🚐 2020 Yetti Grand Escape GE821-KPF — four-season trailer, delivery available

Enclosed insulated underbelly, Arctic package rated to −30 °C, propane and electric furnace, and it sleeps seven to eight comfortably. Message us on RVezy with your dates and your campground, and we will tell you whether the site has power — which, as above, changes the entire fuel plan.