Assuming you are not out to set a speed record on the 7 summits and your goal is more about livable temperatures, stunning sunrises and safe international travel, here’s the best times of year to climb the peaks.
Starting with the easy ones, at least as far as fitting them in, you can pretty much schedule an ascent of Kosciusko and Carstenz at any time of the year.

Though there are seemingly ongoing challenges with accessing Carstenz, and while companies may optimistically have dates scheduled far in advance, rebel activity may be what really dictates your timing.

We will start at the Equator with Kilimanjaro and Carstenz – where it is more about rainy seasons and small temperature variations. In reality, both these peaks can be climbed any time you want.
For Kili, January – March and June – October are normally drier. But with the summer season also seeing more Northern Hemisphere travelers, the more common routes get busier. So you have a choice of perhaps better weather, but more people, or a bit of rain low and snow high – but fewer people.

For both Kilimanjaro and Carstenz, significant snowfall is not unheard of, and the rain in the jungles below can cause as much of a challenge as the snow above. Success rates on both peaks are generally very high – the advice is to just pick a time and go.
Kosciusko, despite its diminutive nature, can be a pleasant stroll in the summer, or you may end up in a complete white out with howling blizzards in the winter.
Peter Hillary relates his climb with Rob Hall and Gary Ball when they faced full alpine conditions that turned their gentle stroll into a battle to get across the slopes and even find the top.

The advantage of winter is you can take in some very fun sking in Australia in the aptly named Snowy Mountains, and at any time of year you can celebrate back at the opera house in Sydney. Not a bad way to round off the trip down under.
Mount Elbrus has the classic northern Hemisphere season, with ascents commonly made from May through September. Its height means it can easily get blasted any time of the year, allowing a few extra days can solve the problem of having to make a completely separate trip back. Of course there are just a few challenges with access right now, and this could well be off the list.

It is a fair question if for now you can’t just ascend Mt. Blanc, a more interesting climb with many fine routes to choose from. While you could pick the popular summer season, in reality there are so many options and routes, with the summit attained in any month of the year by many, that avoiding the crowded huts and tourist strewn slopes may be preferable in any case.
On Elbrus should you get there, the new Leaprus Huts provide a not uncomfortable option if the budget stretches a bit. A very recent report confirms the accommodation, setting and food as good as it looks, so not a bad place to be storm bound.

Aconcagua can be best done in the Southern Hemisphere summer, December – February. The famed Viento Blanco, the white wind, that can strike at any time keeps you from getting complacent. And the trail, similar to Kilimanjaro, facilitates rapid ascents to altitude at an unhealthy pace.
If looking for a winter challenge, the lack of support, mules, rescue options and people in general makes a winter ascent of Aconcagua a completely different proposition. High winds keep the slopes icy or rocky to an extent where the skiing option never really comes into play. Could be brutal, lonely and very interesting.

When it comes to Denali, its Arctic weather and winds seemingly blowing in from the North Pole, leave only a short season for climbing. While some go in early May, the chances of frostbite and extreme cold are higher, and most target summit dates from 5 – 15 June. Going earlier you have better glacier conditions and crevasses are mostly covered and better bridged.

Later in the season you gain the warmth, but house sized crevasses, weak snow bridges and the glacial heat can create a truly fearful descent. Talking to guides however, the weather is variable enough year by year, that a good dose of luck is what is really needed.
If you want the wilderness experience, like all the 7 summits, just pick a different route – or go in winter, as recounted in one of the truly classic Denali books, Minus 148.

Everest – with so many books, stories and stats – is a pretty easy one – you go to summit in May. Now you can acclimatize on other peaks, live in an oxygen tent and arrive just days before you head up the hill. Though going faster may end up costing you over twice as much.
Or you can take the traditional approach and wander gently up the Khumbu from early April, and then back down through the Rhododendrons in late spring, pausing for Chang in Sherpa villages to celebrate your ascent. On the North, the season is the same, perhaps a bit later for summiting as winds are more prevalent and last a bit later into the season.

For more Everest adventure and no company, pick any other season or any other route and you will be up for a real wilderness experience – though Everest has now been summited in every month of the year, which inspires all kinds of adventurous options.
