Symptoms show up inside the first 24 hours and are usually worst after the first night’s sleep. Headache, nausea, no appetite, broken sleep. If your child wakes on day two feeling awful, that is the textbook pattern rather than a bug they picked up on the plane, and the answer is to not go higher that day.

Children are at roughly the same risk as adults, possibly slightly less. The catch is that small ones cannot tell you. Watch for unusual fussiness, going quiet and unplayful, pale skin, refusing food, and sleeping much more or much less than normal. Short rapid breaths with pauses during sleep are a normal adjustment and not the alarm.

Do not book the ski lesson or the big hike for your first full day. Hard exertion before you have adjusted is what turns a mild headache into a ruined week. Give it a day of pottering about. This is the advice families ignore most and regret most.

Drink steadily and eat even when nobody feels like it. The air is dry as well as thin, so you lose water faster than you notice. Appetite drops at altitude, and a child who has not eaten is a child who will feel worse by the afternoon.

Know the numbers you are actually asking your family to handle. Denver 5,280 feet. Estes Park 7,522. Breckenridge 9,601. Leadville 10,119, the highest incorporated city in the United States. Trail Ridge Road tops out at 12,183 and the summit of Pikes Peak is 14,115. That last pair are day trips, not places to sleep.

Going down is the treatment. If someone is genuinely unwell, losing a couple of thousand feet of elevation usually fixes it faster than anything else you can do. In Colorado that is almost always a short drive, which is a real advantage this state has over more remote high places.

Timed entry is in force for 2026 and there are two different permits. The Bear Lake Road Corridor permit covers 5am to 6pm and gets you the corridor plus the rest of the park. The Rest of Park permit covers 9am to 2pm and specifically excludes Bear Lake Road. People buy the cheaper mental model, turn up at Bear Lake, and get turned around.

The dates are not the same for the two permits. Bear Lake Road runs 22 May to 19 October 2026. The Rest of Park system ends earlier, on 13 October 2026. Outside those windows you just drive in with your entrance fee and no reservation at all, which is the quiet argument for going late in the year.

Reservations release on the first of each month at 8am Mountain Time. 1 May opens 22 May to 30 June. 1 June opens July. 1 July opens August, and so on to 1 September for October. Put the release date in your calendar with an alarm, because summer Bear Lake slots go quickly.

The permit itself is only a 2 dollar recreation.gov processing fee. That is not the entrance fee, which is separate. Your permit gives you a two hour window to enter and no set time to leave, so the pressure is on arrival only.

Trail Ridge Road is the drive, and it is seasonal. It reaches 12,183 feet and is closed to through travel from about mid October to late May. July through September is the reliable window for the whole road. If your trip is late May or early June, check before you build a day around it.

Elk are the wildlife you will actually see, and September into October is the rut. The bulls bugle, which is a sound children do not forget. Keep well back. This is the one wildlife rule people break in Rocky because the animals look calm from a car.

The normal Rocky Mountain entrance fees are 30 dollars a vehicle for one day and 35 for seven days. A motorcycle is 25 or 30. On foot or by bike it is 15 for a day and 20 for seven. The park’s own annual pass is 70 dollars. Those are the same for everybody regardless of passport.

The surcharge is 100 dollars per person, not per vehicle, and it applies to non residents aged 16 and over. Green card holders and permanent residents are exempt. It applies per park visit rather than as a one off. Two visiting parents at Rocky Mountain are therefore looking at 35 dollars for the car plus 200 dollars on top.

Here is the bit that saves families real money. The surcharge does not apply if you are admitted on an America the Beautiful annual pass. The non resident annual pass is 250 dollars, up from 80. US residents still pay 80. So for an international family the 250 dollar pass is cheaper than paying the surcharge twice, and it then covers every national park in the country for a year.

At drive in entrances, everyone in the pass holder’s vehicle comes in under that pass. One 250 dollar pass, one car, whole family through the gate. At walk in entrances residency is assessed person by person instead, so arrive by car if you have the choice.

Not every Colorado park is on the list. Great Sand Dunes is 25 dollars a vehicle for seven days, 20 for a motorcycle, 15 per person on foot, and its own annual pass is 45. It is not one of the eleven, so there is no surcharge there at all. That gap is worth knowing when you are planning which parks to prioritise.

Bring photo identification to the gate. Residency is being checked rather than assumed. If you are a US resident travelling with an accent and no ID, you are the person who ends up arguing at a booth with a queue behind you.

I-70 west out of Denver is a predictable weekly jam, not bad luck. On the 65 mile stretch to Silverthorne, a Friday afternoon between 4 and 5:30 turns a 1 hour 25 minute drive into 1 hour 50. Sunday afternoon coming back is far worse. Between 2 and 6 it runs about 2 hours 30 against 1 hour 15 in clear conditions.

In ski season Saturday morning is its own problem. Heading up between 7 and 7:30 takes close to two and a half hours instead of an hour and twenty five. Coming back down between 3 and 4, when the lifts close, adds roughly 45 minutes. Leave before 6:30am or come home after 6pm and you skip nearly all of it.

Denver to Vail is about 100 miles and 2 to 2 and a half hours when nothing is wrong. Winter storms, weekend ski traffic or summer roadworks can add anywhere from 30 minutes to over 2 hours. If you have a flight, build in a full extra hour and do not negotiate with yourself about it.

Denver airport to Estes Park, the gateway to Rocky Mountain, is 76 miles and about 1 hour 26 by the toll road. Through Boulder with no tolls it is 81 miles and about 1 hour 48. Estes Park sits at 7,522 feet, so this drive is also a 2,200 foot altitude gain in ninety minutes.

You can skip a car for the Denver part entirely. The RTD A Line runs from the airport to Union Station, 23 miles in about 37 minutes for 10 dollars each way, every 15 minutes between 5am and 8pm. For a first night in Denver before you collect a hire car, this is the easy move.

Winter tyre rules on the mountain corridors are real and enforced. If you are hiring a car between roughly September and May, take the all wheel drive rather than saving forty dollars on a saloon. This is the actual reason one car in five here is a Subaru, and Adam wrote a whole post about that once because he could not believe it.

Peak single day lift tickets for 2026 reach about 299 dollars at Vail, 269 at Aspen Snowmass and 229 at Breckenridge. Buying online in advance rather than at the window takes roughly 50 to 65 dollars off. A walk up ticket on a holiday week is the most expensive way to do anything in this state.

A full ski day per person lands somewhere between about 194 and 428 dollars once you add the lift, rental, food and parking. Multiply that by five and you can see why a week of skiing costs what a fortnight in Europe costs. I am not saying do not do it. I am saying know the number before you commit.

Rent your gear in town, not at the resort. A resort adult package runs about 72 dollars a day and a child aged 6 to 12 about 45. Town shops run closer to 48 and 30, and pre booking online drops it again to about 42 and 26. Same skis, a ten minute walk, roughly a third off.

Season passes change the maths if you are going more than about four days. The Epic Pass is around 949 dollars and Epic Local 695. Ikon Base is about 719 and the full Ikon 1,179. For a family of five that is a big commitment, but for two adults skiing a full week it can beat day tickets.

Now the summer version. Garden of the Gods is free. Great Sand Dunes is 25 dollars a vehicle. Rocky Mountain is 35 for seven days plus a 2 dollar permit fee. That is a full week of headline attractions for under 65 dollars per car. The mountains are the same mountains. Only the price of standing on them changes.

The one summer splurge worth it with children is the Durango and Silverton narrow gauge railroad. The 2026 season runs 2 May to 1 November. Standard coach is 118 dollars for an adult and 108 for a child aged 4 to 11. It is about 7 hours 15 all in, three and a half hours each way with a two hour stop in Silverton. Under fours who do not take a seat ride free.

Best overall: September into early October. The aspens turn gold, the elk are bugling, the crowds have gone back to school, Trail Ridge Road is still open and the Rest of Park permit system stops on 13 October. Warm days, cold nights, and the light is extraordinary. If I could pick one fortnight, it would be the back half of September.

Good: late June through August, with one caveat. Everything is open, the high roads are clear and the days are long. But July alone brings over 734,000 people into Rocky Mountain, and afternoon thunderstorms above the treeline are a genuine hazard rather than an inconvenience. Start early, be off the high ground by early afternoon.

Ski season: December to March, at maximum cost. Christmas and the New Year fortnight are the most expensive days of the Colorado year. If you want snow and not the price, late January and early March hold good conditions with far smaller crowds and lower rates.

Awkward: April and May. The ski areas are closing, the high roads are still shut, Trail Ridge is under snow and the lower trails are mud. It is the cheapest time to be here and there is a reason. Locals call it mud season without affection.

One date to know if you want the sand dunes at their best. Medano Creek flows at the base of the dunes in late spring and early summer, which turns the whole thing into a shallow beach with mountains behind it. That is a completely different day out from dry sand in August.

Build the trip low to high and never the other way. Two nights in Denver at 5,280 feet, then Estes Park at 7,522, then higher if you are going higher. Flying into Denver and driving straight to Breckenridge at 9,601 feet on the same afternoon is the single most common way families wreck their own week.

The sun at altitude is much stronger than the temperature suggests. Thin air filters less. Children burn on cool days here in a way that surprises people from sea level, and a hat and proper sunscreen matter more in Colorado in September than they do on a beach.

Afternoon thunderstorms in summer are a schedule, not a surprise. Above the treeline there is nowhere to shelter and lightning is the actual risk. Do the high hike in the morning. Plan the town, the pool or the museum for after two.

Hot springs are the great Colorado children’s day and they are open all year. Glenwood is the big one at over two blocks long, roughly 42 to 60 dollars for adults and teens and 30 to 38 for children. Sitting in hot water in falling snow is the thing they will actually describe to their friends.

Not everything has to be a mountain. Casa Bonita in Lakewood is cliff divers, a mariachi band, a gorilla and sopapillas, and the food is genuinely beside the point. We went when we lived there and I still quote my own conclusion at people. The lower your expectations, the more fun you will have. It is now ticket only with no walk ins, so book ahead and check the current price.

Pack for a thirty degree swing in one day. A September morning in Estes Park can start near freezing and hit the seventies by lunch. Layers for every person, and a proper jacket even in August if you are going high.

It suits families with children roughly six and up. That is the age where a real hike, a sledding run down a dune and a full day on a train stop being endurance events and start being the best day of the holiday. The scenery does a lot of the work for you.

It suits families who want outdoors without roughing it. Denver is a proper city with a proper airport, the mountain towns have good food and comfortable beds, and you are rarely more than an hour from a hospital or a supermarket. It is wilderness with a safety net, which is exactly right for a first big outdoors trip.

It suits a summer budget better than almost anyone expects. Free parks, cheap entrance fees, and hiking that costs nothing. Outside ski season this state is far kinder to a family of five than its reputation suggests.

Skip it with a baby or a toddler if you were planning to go high. A small child who cannot tell you their head hurts, at nine thousand feet, on a trip you have paid for, is a bad combination. Stay on the Front Range or wait a few years.

Skip a winter trip if the budget is tight. There is no clever way to make a peak week of Colorado skiing affordable for five people. If snow is the point and money is the constraint, go in March, or go somewhere else, or come in summer instead.

Skip it if anyone in your party has a heart or lung condition without talking to a doctor first. This is not a scenic preference, it is a medical one. Altitude is a real physiological load and it deserves a real conversation before you book.

Utah is the drier, redder, stranger version. Five national parks close together, less altitude stress because much of it sits lower, and scenery that looks like another planet. If your family found Colorado’s green mountains familiar, Utah will not be familiar at all.

Wyoming is Colorado with fewer people and more animals. Yellowstone and Grand Teton are both on the 100 dollar surcharge list too, so the same annual pass logic applies. The driving distances are longer and emptier, and the wildlife is on a different scale.

New Mexico is the cultural trip rather than the outdoors trip. Santa Fe and Taos are a few hours south of the Great Sand Dunes and pair naturally with a southern Colorado loop. We drove through Taos on a road trip once and it is a genuinely different country down there.

Florida is the exact opposite holiday and worth naming as a contrast. Flat, humid, engineered, indoors when it rains. Colorado is high, dry, unpredictable and outdoors by default. Families who find theme parks overstimulating almost always prefer this state, and the reverse is just as true.

The 300 days of sunshine claim is marketing, not weather. Denver averages about 86 days a year with measurable rain or snow, which leaves roughly 279 without. The figure traces back to railway companies in the 1870s trying to persuade workers to move west. It is sunny here. It is not 300 days sunny.

Some of the best things are free. The Coors tour in Golden was free when we went, self guided with an audio handset through a five mile facility turning out sixteen million barrels a year. Garden of the Gods is free. A lot of what makes Colorado good does not have a ticket price.

Green chile goes on everything and it is not Mexican food exactly. It is its own regional thing, it is on burgers and breakfast burritos and eggs, and asking for it smothered is the correct answer. This is the flavour I actually missed after we left.

There are 58 peaks over fourteen thousand feet and climbing one is a normal weekend here. Not for your family on day two, but it explains the culture. Everyone you meet is training for something, and the trailhead car park is full at 5am.

Alcohol hits noticeably harder at altitude. One drink in Breckenridge does not feel like one drink at home. Worth knowing on the first night, which is also the night you are least adjusted.

The Subaru thing is not a stereotype, it is a census. Adam counted roughly one in five cars as an Outback or an Impreza when we lived there, and then wrote a post about it because he did not believe himself. Roof racks, bumper stickers, the lot.