May and September are the most pleasant months, when outdoor cafes and beer gardens are open and busy. Rain is always a possibility, but not constant enough to thwart your plans. The numbers of tourists can be high.

May to March and October to early November also have plenty of mild and nice days, with the advantage that tourist crowds are somewhat smaller.

November and early March brings greyer skies and colder temperatures. Keep in mind that in the dead of winter there are only 6-8 hours of daylight and in December, the sun sets arount 3:30pm. If you're not headed to a winter resort, the tourists are sparse.