The Norway of picture books isn't so much a region as a ribbon, wrapping from southwest to northeast around more than 1600km/1000 miles of coastline. Off the west coast lies some of the world's warmest high-latitude water. This part of the Atlantic basin never freezes, even during weeks of winter darkness. The ocean currents that bring warmth here from the Gulf Stream and its northern extension might get diverted someday, but for now, they help shape Norway's uniquely varied and changeable weather.
Like spokes on a wheel, the fjords carved out by melting glaciers slice through Scandinavia's mountainous spine at angles facing the sea. That makes them convenient for intercepting gales and squeezing out moisture. From October through January, the west coast as far south as Stavanger gets substantial rain or snow about 2 out of every 3 days. The higher terrain along the coastal strip gets more than 3000mm/118in of precipitation a year – much of it snow – with almost twice that amount falling in favoured spots such as near the Nordfjord area. The coast itself alternates between cold rains and wet snows. Drier air that's chilled over the higher terrain often cascades down into the fjords, making the inner valleys notably colder than the immediate coast. When Siberian air pushes into Sweden, it can spill over the mountains and enhance the downfjord flow, making for crystal-clear skies overhead while producing “sea smoke” fog offshore.
In summer, gentle sea breezes help keep the fjord country cool, outside of rare hot spells that can reach as far north as Tromso. Most coastal towns see only about a third of daily sunlight, no matter what time of year it is. Thus, although visitors can't expect non-stop sunshine in July, there's a good deal more sun on most of the extra-long summer days than during winter. The steep-sided fjords get less sunshine than the open coast or the highlands. Showers (mostly light) occur about every other day in mid-summer, and the more substantial autumn rains begin as early as late August. The Finnmark coast stays quite chilly even in summer and gets wildly stormy in winter as coastal lows sweep by. Eastern Finnmark is lucky to get more than two weeks of clear skies a year.
On the other side of the mountains, southeastern Norway has a more Swedish-flavoured climate. Parts of the upper Randsfjorden are almost semiarid, with the average yearly precipitation as low as 300mm/12in. Snowfall in the Oslo area is frequent but may amount to little more than flurries. Some winters are markedly colder or wetter than others, however. Relative mild spells, borne on southwest winds from the Atlantic, are offset by intrusions of bitter Arctic cold. Early spring is especially prone to Siberian air masses; they're in place on about half the days in a typical March and April, often resulting in frigid mornings but bright, sunny afternoons. June and July can be thundery but with more sunshine and warmth than the west coast gets. Occasional strings of bright days can bring readings above 30°C/86°F.