September is a great month for Airstream travel in most of the USA and Canada. Fall foliage starts to appear in the northern states, the worst heat of the summer is usually waning in the low elevations, and you don't yet have to start worrying about snow squalls in the western mountain passes.
October is pretty good too, but by mid-month in the northern New England states you'll start to see campgrounds shut down due to persistent overnight freezes.
By mid-November, conventional wisdom says that it's probably time to winterize your Airstream until the next season.
Why we prefer unconventional wisdom
"Shoulder seasons" are golden opportunities to finally visit the places you've always dreamed of visiting. I'm talking about the major National Parks and those impossible-to-reserve state parks that everyone packs into during the summer. They're often wide open and waiting for you to book a stay in November or early December.
The shoulder seasons also mean that there are fewer mosquitoes and other flying pests (usually none at all). Tours, popular trails, and overlooks aren't as crowded. Premium campsites are ripe for the taking. Fees are sometimes lower, and in National Parks you'll often find the staff less harried and more interested in chatting with you.
Plus, in fall and in spring you will often experience more dramatic skies, due to the changing weather. Sunset and dawn become more colorful. If you are a photographer, this alone might be reason enough to accept a few frosty nights.
Some of our favorite shoulder season spots
In Rocky Mountain National Park, you might arrive in time for the famous elk "bugling" season. In Olympic National Park you'll experience over 100 inches of steady gray rain falling at the Hoh Rainforest campground, which is a surprisingly relaxing (almost Zen) experience. And in Zion National Park, you'll avoid the crowds and the tent caterpillars that famously swarm the campgrounds in April.
Waiting for elk in October, at Rocky Mountain National Park
At Mesa Verde National Park you'll find it's easier to book one of their essential cliff dwelling tours. Great Smoky Mountains National Park, the most visited park in the country, will be more accessible (but still popular).
Acadia National Park in Maine has developed a reputation for being crowded in recent years, but if you go in October or November you'll find the crowds mostly gone, the beaches empty, and the best hikes mostly to yourself. Just be aware that the park campgrounds close mid-October and most of the park roads close Dec 1.
Falling rain and fairy-like forests at Olympic National Park in October
How to have a successful off-season experience
Here are five strategies I use when camping off-season:
1. Aim for the popular spots
If you're going to put up with a little chilliness, you might as well go for the most unobtainable places you can, for as long as you want. Think big. For instance, instead of fighting for a campground for a day or two in Yosemite, hit the park in late September and stay for a week.
November hiking in Yosemite
2. Always check the official websites when planning
It's easy to find out what to expect. First, go the official website for the park or campground you're visiting. You need to know what temperatures to expect, which roads may be closed, whether the campgrounds will have services, etc.
NPS.GOV is your best friend when it comes to National Parks, and most State Park services have decent websites as well.
In particular, you need to know about the weather. If the official site doesn't have good guidelines for what to expect during each month of the year, just search for "xxxx park weather November" (or whatever month you expect to be traveling) and you'll get an idea of the range of temperatures to expect.
3. Out west, keep in mind altitude is everything
Crater Lake National Park is only 65 miles from Medford, Oregon, but these two places don't have the same weather. One is at 1,380 feet elevation and the other is at 6,178 feet elevation. Crater Lake will be locked and snowed in for the season usually before the folks in Medford have finished putting up their Halloween decorations.
Summer (yes, summer!) at Crater Lake National Park
And if your route involves a high mountain pass, it's very important to check for advice about the risk of snowy conditions. If in doubt, wait it out. Motorhomes and trailers aren't great in snow and ice.
4. Work around the holidays
Everyone wants to visit a nice place at Thanksgiving and Christmas. But the week after Thanksgiving is usually dead almost everywhere, right up to about a week before Christmas.
And that's exactly when we're heading out for a 2-week tour of Grand Canyon, Lake Powell, Zion, Valley of Fire State Park, Big Bend of Colorado State Park, and a few other choice spots. Early to mid-November is often a great time to travel, too.
5. Be well supplied
In the off-season a lot of services, stores, and even roads may be closed. Arrive loaded for complete independence, with plenty of food, water, electricity (solar panels, generator, or expanded battery bank), propane gas and fuel for your tow vehicle. Don't count on buying anything at your destination.
Likewise, pack for a wide range of weather conditions. You should have everything from sandals to winter hats. You don't have to load up the Airstream with everything you own, but be sure to have at least one of everything to account for any type of weather.
If you take the season less traveled, you'll find yourself being one of the "lucky" Airstreamers who can talk about their extraordinary and leisurely visits to places that other people struggle to see in the peak vacation periods. Traveling off the peak is how knowledgeable Airstreamers get to see more places and enjoy a more relaxed pace.