Mauna Loa day hike via the Observatory trail

A little background about Mauna Loa

At 4169 m Mauna Loa is the second highest peak on the Island of Hawai’i. It’s also the tallest and most massive mountain in the world. While there’s a road all the way up to its neighbor Mauna Kea (at 4205 m the highest mountain on the island), getting to the top of “the long mountain” is a bit more of a challenge.

Let’s quote my guidebook for a moment:

Getting to the top of Mauna Loa is tough, no matter which way you slice it. […] You can do it the hard way or the very hard way – it’s your choice.

The hard way is a 3-5 day hike. I only spent five days on the island, so this option was out. I had to look into the second one:

The other way is a tough 13-mile-round-trip day hike from the Mauna Loa Weather Observatory off Saddle Road. […] count on altitude sickness from starting so high […] you can do it in a day, if you’re into punishment […] It’s always cold up there, and snow can come any time of the year without warning. Altitude sickness is common, even among the fittest.

This comes from one of the best guide books, I’ve ever used and folks, who don’t seem to dramatize things. I also met a Scandinavian hiker on Mauna Kea, who told me he tried the hike the day before, but had to turn around, mainly because he didn’t bring the right shoes. I wouldn’t have wasted much thought about this, but he also told me he summited Cho Oyu (8201 m) in winter. Having someone with that experience say the hike you plan is tough, makes you wonder, if it’s really such a great idea.

I did some research about it and basically had three concerns: length, weather and altitude.


The trail is about the distance of a half marathon (return) and the official sign at the beginning of it puts the summit hike at 10-12 hours, most tour guides list it at 10 hours, while some guys obviously do it quite a bit faster. I’m not a slow hiker, so I was confident, that even in the worst case I would be down before sunset as long as I start early enough (sunrise is around 7 am).


The weather is a bit more tricky. The clouds, that build around Mauna Kea and Mauna Loa almost every afternoon, give you an idea of how foggy, cold and uncomfortable it can get. And while it feels surprisingly warm in the sunshine, temperatures still drop well below freezing not only at night. In short, I made sure to check the weather report to pick a clear day for the hike, but also prepared for the worst (brought my winter hiking gear). During my ascent I learned, that there are some hideouts, that allow you to sit out a storm, but I definitely don’t want to try this.


The biggest challenge is the altitude. 4000 m is not high compared to other mountains and if you’re well acclimatized it really shouldn’t be a big deal at all. The trouble on Hawai’i is, that a lot of people (including me) don’t have or don’t take the time to do that properly. Most of the places to stay are along the coast and around sea level. That means, if you don’t camp at higher places, your body will have to endure an altitude difference of around 4000 m in just a couple of hours.

My lame attempts to get at least some acclimatization were visits to the Mauna Kea Visitor Center (2804 m) and Mauna Loa Observatory (3370 m) as well as the Mauna Kea summit (4205 m). I tried to spend as much time there as possible, but everything was still done by car in quite rapid pace. I visited the start of the hike near the Mauna Loa Observatory the day before my summit run. The reasonable choice would have been to camp there for the night (probably in the car). I decided against it and went back to sea level to spend the night. If you want to enjoy all of your summit day, DON’T DO THAT!

The most important thing at high altitude is to drink enough. The air is dry and there is no water on the mountain, so prepare for carrying ridiculous amounts (I think I used somewhere around 6 liters during the hike). I had a small water bottle in my hand and was drinking from it almost constantly. Whenever it was empty, I refilled it from one of the larger bottles from my backpack. I also used chewing gums (supposed to help with the difference in air pressure) and low dosed aspirin pills to prevent and ease some of the symptoms of altitude sickness.

There’s water with added oxygen, that’s been advertised for some years now. Maybe hiking in altitude could be a use-case for it. I only thought about it during my hike, so I didn’t try it. Then, of course, there’s also all forms of bottled oxygen (as the social media guys of one company pointed out to me after posting my summit photo to Instagram), but that’s probably a bit over the top for anything lower than the Himalayans. It will help for sure, but better spend more time for acclimatization instead.

The hike

I started at 4:45 am and drove up Saddle Road to the Mauna Loa Observatory road. This is a narrow 28 km road winding up to the Observatory through endless, very impressive lava fields. The road has been repaved recently, so it’s quite enjoyable to drive, but you need to be careful at the various blind spots (although traffic coming down the mountain is very unlikely so early in the day).

After arriving I prepared for the hike and started shortly after the 7 am sunrise. The hike starts right where the street ends. You follow a dirt road for some minutes before the trail turns to the left and south up through old lava. This is what it will look like for most of the hike. The trail leads through interestingly shaped lava formations and is mostly marked only with rock cairns (ahu), which are clearly visible in good weather. For some parts you will follow an old dirt road or a comfortable trek over greenish looking sand. However, most of the time you struggle through harsh and rather unforgiving lava terrain.

I didn’t know how the altitude would effect me, so I started slower than usual, making sure not to over-pace.

After about 6 km there’s an intersection with the trail to the Mauna Loa Cabin. I followed the 4 km long Summit Trail to the top of the mountain. It’s a long, very gradual accent and I started to feel the effect of the altitude (or let’s say my lack of acclimatization) somewhere around the 4000 m mark. I got a minor headache and realized, that calculating the remaining time to the summit (based on my average speed and the distance still in front of me) suddenly became a very challenging task. Everything takes a bit more time at “high” altitude. I was relatively close to the summit, so I decided to push through and only turn around, if my condition got worse. Shortly before the summit I got the first view down into the huge crater. It’s a big WOW moment and worth all the struggles to come here.

A couple minutes later (around 11 am) I reached the summit. I took some pictures and then quickly headed down again.

Descending the Summit Trail was tough. The signs of altitude sickness got worse and the trail stays around 4000 m altitude for quite some time, giving you no option to loose height as quickly as you might wish. In a moment of carelessness my foot got stuck under a rock and I fell face forward onto the hardened lava. My hands could stop most of the fall and I got away with some minor bruises and cuts (lava rock makes some nasty scars). After that incident I slowed down again and eventually reached the old dirt road at around 3800 m. From there on it was an enjoyable hike again and I started to realize my accomplishment. In a good steady pace I reached the Observatory around 2:30 pm. I took 4 hours to ascend and 3,5 for returning down. If you know the trail, are reasonably fit and well acclimatized, I’m sure this can be done a whole lot faster.


This hike was a very humbling experience. The landscape is breathtaking and beautiful. The scale of Mauna Loa is still hard to grasp, but hiking (and driving) on it for so many hours starts to give you an idea just how large it really is. It’s not a difficult hike and at lower altitudes this could almost be a “walk in the park” kind of thing. The altitude and remoteness makes it challenging nevertheless. It’s also worth mentioning, that I didn’t meet a single person on the mountain all day (and it was a beautiful, sunny Saturday), so this is really quite a remote and lonely place to explore.

Surprisingly, I didn’t feel much muscle fever the days afterwards, but I had a general feeling of being worn-out and tired the day after the hike. Everything below 3900 m was wonderful, above that it was tough for me (but that’s just the missing acclimatization). All in all, it was a great experience and I’m glad, I gave it a try.