The weather in Northern Europe in early Spring (Apr-May) will see temperatures between the mid-40s to mid-60s with a third of the period experiencing some rainfall. The perfect weather for sweaters and sweater "jackets" with full length zippers for easy removal. I prefer t-shirts over regular shirts and will add a couple of polo shirts if I need to dress it up a bit. Unless you are attending opening night at the Opera or prefer the James Bond look of a tuxedo this should suffice for almost all occasions.

You'll be doing a lot of walking so good shoes and socks are a must. If you plan to bring sandals, you'll need to ration their wear so as not to experience any foot issues. I prefer rain proof low top hiking shoes. The important step is to make sure they are broken in and consider high quality insoles like Superfeet ™ or similar brand.