It's never been so hard getting ready in the morning as it was in my first month in Hamburg. Coming from Central Europe you experience every kind of weather but none of them is really permanent. Not like the rain in Hamburg. It's not that it rains all the time but it rains almost every day which requires a specific way of dressing.
I remember during my first week here I met a German guy who after checking out my outfit told me that I will need to buy some new clothes. Well, it didn't take long until I realized that he was totally right. Half of the clothes I brought with me are still hanging in my closet without being worn at least once. So I tried to sum up my experiences after two and a half months in the northernmost metropolis of Germany about what to wear/take with you in a rainy city:
Umbrella! Never forget your umbrella! There is a big supply in the umbrella market but you shouldn't necessarily go for the first one you see. Take the time and energy to choose the right umbrella because you two are gonna be besties for a long time. So, my advice is: try to open and close the umbrella in the store before buying to see if it works properly. And pick one with a color that expresses your personality 
On a cloudy and rainy day it will cheer you up.
Layers! Layers are the key for the perfect dressing. According to my experience it is better to wear more thin layers than big heavy wool sweaters and it is easier to put on/take off one layer according to the temperature. And if you think it over it is actually practical, you can wear more outfits in the same time and just "change" in a second and voilá!
One of the favorite "inventions" are the rain boots and I am so happy that they are in fashion here, not like in my country where it is more associated with the farmer life Rain boots look good, they match everything and they are practical, you can just cross every puddle instead of going around or jumping over them. The only disadvantage is to wear rain boots inside for a long time. So you might want to take a pair of changing shoes with you to the office/school.
And my last advice for today: if you would like to ride your bike in rainy weather, you should get yourself a pair of rain pants. They might not be very fashionable but they are extremely useful.
It is interesting to see that even in such a small continent the dressing practice differs so much.
Do you have any similar experiences? Do you wear anything "extraordinary" in your city/country?