The weather in the mountains is not always as desired (sunny but not too hot, a gentle breeze, an occasional cloud....). Especially the wind is a big issue and is often underestimated - especially in summer! This is where the layer principle pays off from the start. And believe me, as much as you sweat and your face glows when going uphill (especially in midsummer), you will cool down quickly on the summit - within a few minutes because you are no longer moving and there is usually a strong wind blowing on the summit. Since you have sweated and moisture quickly dissipates your body heat in the wind, you will quickly get cold. Put on your jacket before you get cold (so as soon as you arrive at the summit!) and take off the wet shirt and dry it (replacement shirt for the break!). This way, your body can save energy because you still have to go downhill - and you never know what might happen in between. Hypothermia can quickly lead to a situation where you can no longer make rational decisions - even if it is just the decision to take a shortcut because this path is more in the sun or shorter but steeper and more difficult - you tend to become careless. This also applies to hunger and thirst. Read "Eating and drinking in the mountains". Unfortunately, it's often the case that you can't have a leisurely snack at the top of the summit - it's better to put on your jacket straight away, take some great photos and then descend a few meters to a sheltered spot where you can fortify yourself and take a relaxing nap.
Please never underestimate the rapidly changing weather, such as approaching fog or clouds, in which you then walk when you are at the same altitude. Even in an otherwise manageable terrain that you know, you are simply "lost". Your own sense of orientation will eventually leave you because you can only see what is directly around you (most intense in winter - also white below - "whiteout" at its best). So you can no longer recognize dangerous cliffs, hollows, overhangs, etc. You wander around for hours, have little or no water left. You know it will soon be dark and therefore colder than it already is (and no, it's not comfortably warm in the clouds, but cold and humid) - believe me, not a pleasant experience and usually not ending well. If you also twist your foot - not good. And no, the rescue helicopter is not your lifesaver, as it can only fly if the weather poses at least an assessable and justifiable risk to the crew. Summer in the mountains is also thunderstorm time, which means for hikers to get up very, very early to be back in the valley or a protected area by early afternoon.A bit of knowledge about clouds doesn't hurt - simply put, towering clouds are a warning sign, but you can already recognize the signs if they are still forming, then pay attention to the wind direction and don't walk towards the thunderstorm instead of away. If you are not familiar with the weather, it is best to regularly check your weather app on the radar image, so you can see where the weather is likely to go (here I should mention: always enough battery power is worthwhile, especially because it quickly empties in the cold - take a power bank with you). With good preparation, you can minimize many risks - regularly check the weather forecast via various apps and adjust your tour - yes, even if you then don't climb the summit anymore but turn back earlier. You can repeat the tour on another day, even if it's annoying now because you had a long journey and took time off work, etc. Nature will never accept your stubbornness as a reason to take it easy on you. It is simply what it is. Many people think these rules do not apply to them or that they know the route by heart, so not much can happen even in harsh conditions. Or they think that thunderstorms in the mountains cannot appear within seconds - or simply that "it won't be that bad". Be sure, it often gets much worse.
Example of clouds forming in the Grimsel area, the cloud cover rises faster than you think (and you usually still have to descend - in the worst case, directly into it).
Here, there was still a few meters of visibility and I was already below. A banal weather situation, especially in rough terrain, can develop devastating.
