In Norway and Sweden you'll need to be prepared for anything as far as the weather goes. In Summer it can get very hot, but also very cold. And when you cycle over a high plane, the weather can change without warning.
Personal preferences play an important role. One swears at merino wool, while the other prefers Lycra. Important overall is to avoid bringing thick clothing. Using clothing in layers is much more efficient. Generally, cotton is not recommended. It stays wet longer, which cools you off quickly. Polyester (Lycra) fit s comfortable and dries quickly. Clothing made from merino wool is good for any temperature. As well as during cycling (shirt, vest or jumper and socks), and while sleeping (undergarments). It won't stink and dries quickly. Draw back though is it's vulnerability.
An extra jumper or vest is practical, because it can be chilly. Opt for a jumper or vest of fleece or merino wool.
A jacket of Goretex protect against rain, wind and cold, but has sufficient capacity for breathing. Another option is soft shell (keeps the wind out, breathes, and is water-repellent) plus an extra raincoat.
A cycling pants with a pad, absorbs moist, prevents friction and dampers the bumps s bit.
A (zip-off cycling trousers) made of quick drying and breathing material (like from Gonzo of Vaude) can be put on over your cycling pants, but also in the evening when it gets chilly. As long the rain is only very light, you wouldn't need to use a rain trouser. You'll stay warm through cycling, and you dry up quickly anyway. With low temperatures and/or rain throughout the day, an extra rain pants can become handy.
Closed cycling shoes protect your feet against cold, dirt and sharp objects. If you don't cycle with cycling shoes or cycling sandals, then choose a shoe with a hard sole. It provides better power transfer of power from your foot to the bicycle. In rain or extreme cold, you can put on (water tight) shoe covers over it.
- A fluoresce vest is recommended when cycling over busy roads or through tunnels.
- A helmet. Even though a helmet is not mandatory in Norway and Sweden, it is certainly recommended.
- Gloves. With or without fingers. Cycling gloves without fingers provide grip because they take up sweat, but won't protect you from the cold. Gloves with fingers are handy in Norway and Sweden, because in the higher places it can still freeze a little in August.
- Wash or at least rinse the pad in your cycling pants every day to prevent infections.
- Merino only needs to be washed every once in a while. Just leave it hanging outside for a couple of hours and after that it is fresh again.
- Launderettes are scarce in Norway and Sweden, but often a campsite has a washing machine that can be used for a fee.