Nuremberg, where it lies

In Nuremberg, a city in the southern German state of Bavaria, 300 metres (1,000 feet) above sea level, the climate is slightly continental, with cold winters, and mild or pleasantly warm summers.
The average temperature in January is -0.5 °C (31.5 °F), while in July it's 19 °C (66 °F).
Here are the average temperatures.
Nuremberg - Average temperatures
Min (°C)-3-3038121313951-2
Max (°C)3491419232524191474
Min (°F)272732374654555548413428
Max (°F)373948576673777566574539

Precipitation is not abundant, about 640 millimetres (25 inches) per year, but it is quite common and well distributed over the seasons; however, the rainiest season (at least in quantity) is summer, the least rainy season is winter. Rainfall often occurs in the form of short showers or drizzle, whereas during the summer, thunderstorms can break out in the afternoon.
Here is the average precipitation.
Nuremberg - Average precipitation

Winter, from December to February, is cold: daytime temperatures are on average a few degrees above freezing (0 °C or 32 °F), while at night they are a few degrees below.
However, different weather situations can occur.
When the westerlies blow, the temperature can be quite mild, and can reach 10/12 °C (50/54 °F), but there may be wind and rain.
Under the influence of a high pressure system, the weather is cold, the sky is gray and fog can form.
On the contrary, when the city is reached by cold air masses from Siberia, the temperature drops below freezing, for longer or shorter periods, even during the day. The temperature rarely drops below -15 °C (5 °F), however, it can do it on colder periods, which in the past were more frequent. Here are some values recorded in the past: January 1940: -27 °C (-17 °F); January 1941: -21 °C (-6 °F); January 1942: -26 °C (-15 °F); February 1956: -29 °C (-20 °F); January 1963: -25 °C (-13 °F); January 1979: -20 °C (-4 °F); January 1985: -24 °C (-11 °F); February 1986: -18 °C (0 °F); January 1987: -21 °C (-6 °F); December 1996: -22 °C (-8 °F); February 2012: -20 °C (-4 °F).
Snowfalls in Nuremberg are quite frequent, though usually not abundant, and occur in the form of sleet or light snow, sometimes, however, snow can accumulate on the ground, and last for many days.

Spring, from March to May, is initially cold, with possible snowfalls still in March, and then it gradually becomes milder in April and May, although some cold days, with highs around 10 °C (50 °F), can occur also in May, especially in the first half of the month. However, April and May are, albeit slightly, the sunniest months.
Typically, in the second half of May the temperature becomes permanently acceptable, and there can be the first pleasantly warm days, with highs around 25 °C (77 °F) or even above.

Summer, from June to August, is mild or pleasantly warm; Atlantic disturbances can pass also in this season, bringing cool and rainy days, but there may also be some hot and sunny days, in which the temperature can reach 28/32 °C (82/90 °F), however, with some risk of afternoon thunderstorms. More rarely the temperature can even exceed 35 °C (95 °F); the highest records are about 38/39 °C (100/102 °F), however, these heatwaves only last a day or two.

Autumn, from September to November, is initially pleasant, ie in the first half of September, then it gradually becomes more cold, dull and wet. The first night frosts usually occur in November, but sometimes also in October. During calm nights, fog may form.

Nuremberg, castle

The amount of sunshine in Nuremberg is not high in autumn and winter months: the sun rarely shines from November to February, while it goes a bit better in summer: there are on average 7/7.5 hours of sunshine per day from May to August.
Nuremberg - Sunshine

When to go

The best time to visit Nuremberg runs from mid-May to mid-September, being the mildest of the year. July and August are the warmest months; however, it's better to bring a sweatshirt or sweater, a light jacket and an umbrella, for cool and rainy days.