There's no such thing as bad weather, only bad clothing.
Weather is something we cannot change, but how we meet it is entirely up to us. That is the heart of this Scandinavian saying, which turns a complaint into a small practical challenge. Instead of blaming rain, wind, or cold for ruining a day, it suggests that the real problem is usually that we are unprepared. Rain is just rain until we are standing in it with wet socks and no hood.
The saying is usually described as a Swedish or, more broadly, Nordic proverb, so there is no single author to credit. It grows out of a culture that lives with long winters and changeable skies, and that values outdoor life, often summed up by the idea of friluftsliv, or open-air living. It also echoes an older, Stoic-flavored outlook: separate what is outside your control from what is within it, and put your effort into the second. Preparation, not wishful thinking, is how you gain freedom.
In everyday life, you might apply it by deciding not to skip your morning walk just because the forecast looks grim. Put on a waterproof jacket, sturdy shoes, and a warm hat, and the same drizzle that seemed miserable from the window becomes bracing and even pleasant. The idea stretches beyond clothing, too: much of what we call bad conditions may simply be a call to prepare better.