The avalanche danger rating scale can be pretty confusing for a layman. Avalanche danger rating 3 on a scale of 5 doesn't sound too dangerous right? It's right in the middle! So you might think that there isn't much of a risk when skiing off-piste. Let's get straight to the point: avalanche danger rating 3 (Moderate) can be dangerous. About 20% of the snow cover has weak spots and spontaneous avalanches of medium size are possible. The weight of a single skier or snowboarder on the snow cover is enough to trigger an avalanche. Ergo: it definitely can be dangerous. How come?
The avalanche danger scale has two objectives. One objective is to express the risk that a catastrophic avalanche will threat public life (roads, bridges, villages) and the other objective is the probability of an avalanche in the ski areas, that threat skiers and snowboarders. These are two objectives in a single scale.
Rating 4 (High) and Rating 5 (Extreme) are designed to express the risk of a catastrophic avalanche. The purpose is to enable administrations to take action to protect the public life from the devastating avalanches. Off-piste skiing and snowboarding isn't the best idea during those rating levels. Most ski resorts will be shut down completely during avalanche danger rating 5 (Extreme) and some lifts are open with avalanche danger rating 4 (High), but those lifts will only bring you to pretty flat slopes that have no steep faces above them. If you want to go off-piste with avalanche danger rating 4, you should really consider to change your plans for the day. Even for the most experienced freeriders it's really hard to choose the right lines. A total of 40% of the snow cover is considered unstable.
Avalanche danger ratings 1 (Low), 2 (Moderate) and 3 (Considerable) are designed for skiers and snowboarders who want to ride off-piste. So basicly, the avalanche danger rating scale for normal skiers and boarders has just been reduced to three rating levels.
The Swiss institute for 'Schnee- und Lawinenforschung' (SLF) puts it like this:
The avalanche bulletin is intended for all those who are exposed to potential avalanche danger in the mountains in winter, whether engaging in a professional or recreational activity, including those who are responsible for the safety of others. This includes members of the following groups:
The most important thing is that this clearly shows that avalanche danger rating 3 (considerable) is already pretty dangerous for skiers and snowboarders. Don't forget that this avalanche danger rating claims 54% of the avalanche victims in Switzerland. And according to the SLF, the long-term (20-year) annual average number of avalanche victims in Switzerland is 23. Accident analyses show that most avalanche victims come to grief in open terrain; that is to say, while engaging in leisure activities on skis, snowboarding, or taking part in mountain climbing or similar pursuits. This group's share of fatalities between 2002/03 and 2011/12 was more than 90%. Of these victims, about 90% triggered the avalanche themselves or it was released by another member of the same group.
Like I said, the avalanche danger rating scale can be pretty confusing. Especially when you're not an expert. If you don't have the right knowledge or if you don't know that you can make the right decisions in the backcountry: go out with a mountain guide! If you want to learn more about the risks of skiing and snowboarding in the backcountry and how to manage those risks: check out the Mountain Academy.