Map from Google - Munich

In Munich, capital of the state of Bavaria, located in south-eastern Germany, 500 metres above sea level, the climate is continental, with cold winters, and mild or pleasantly warm summers. Due to its location away from the sea and close to the Alps, the city is exposed to cold waves, so it is often the coldest city in the whole Germany, while in summer it is subject to thunderstorms. The city is also subject to the Föhn, a warm and dry wind that descends from the mountains (the Bavarian Alps in the south, which become clearly visible when this wind blows, because of the clearness of the air), and is capable of causing a rapid increase in temperature and a decrease in relative humidity; this wind is most common in autumn (but it can also blow in winter and spring).
The average temperature in January is 0 °C, while in July it's 18.5 °C.
Here are the average temperatures.
Average temperatures - Munich
MunichJanFebMarAprMayJunJulAugSepOctNovDec
MunichJFMAMJJASOND
Min (°C)-3-3148111313951-2
Max (°C)3491419222424191474

Precipitation is quite abundant, close to 1,000 millimetres per year, thanks largely to the May-August period, in which precipitation exceeds 100 mm per month, because of afternoon thunderstorms; for this reason the rainiest season is summer, while the least rainy season is winter. In other seasons the rain falls often in the form of short showers (sometimes even of snow), of drizzle or light snow.
Here is the average precipitation.
Average precipitation - Munich
MunichJanFebMarAprMayJunJulAugSepOctNovDecYear
MunichJFMAMJJASONDY
Prec. (mm)504560709513013011085657060965
Days1091111121412111091111129

Winter, from December to February, is cold: the daytime temperatures are on average a few degrees above freezing, and at night a few degrees below.
However, different weather situations may occur.
When the westerlies blow, the temperature remains above freezing during the day, and around freezing at night; rain can fall during the day, and even light snow in the coldest hours.
When the Föhn blows, the temperature can exceed 10 degrees, and it can sometimes be mild even at night.
In anticyclonic days, the weather is cold, the sky is gray and there may be fog, and sometimes the temperature remains below freezing even during the day. Fog is more frequent in the northern part of the city.
On the contrary, when the city is reached by cold air masses from Russia, the temperature drops below freezing, for longer or shorter periods, even during the day. Minimum temperatures around -15 °C are not so rare, and during the coldest winters, which in the past were more frequent, they can drop below -20 °C (here are some values recorded in the past: February 1929: -31.5 °C, March 1929: -20 °C, February 1940: -24 °C; January 1942: -30 °C; January 1947: -27.5 °C; February 1956: -28 °C; January 1985: -27.5 °C; February 1986: -23 °C; December 1996: -20 °C; February 2012: -22 °C).
Snowfalls in Munich are frequent, and often occur in the form of sleet or light snow, but sometimes they can be abundant.

Spring, from March to May, is initially cold, then it gradually becomes milder, but with possible returns of cold, and late snowfalls and frosts, still in April. Some cold days, with highs around 10 °C and lows around zero, can occur also in May, especially in the first half of the month. In sunny days, in April and May the temperature during the day can become mild, or even warm, but the daily temperature range is often considerable, so that nights can remain a little cold.
Typically, in the second half of May the temperatures become permanently acceptable, and there can be the first pleasantly warm days, with highs around 25 °C or even above.

Summer, from June to August, is pleasantly warm during the day, but with clear skies nights can be cool, and sometimes even a little cold. Atlantic disturbances may still pass in this season, bringing cool and rainy days, though less frequently than in northern Germany. There may also be some hot and sunny days, in which the temperature can reach 28/32 °C, however with some risk of afternoon thunderstorms, sometimes intense and accompanied by hail. More rarely, the temperature can exceed even 35 °C.

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, while the Föhn can bring mild and clear days.
During the Oktoberfest, which is held in the last two weekends of September and the first of October, you can expect minimum temperatures around 5/8 degrees and maximum temperatures around 15/18 °C. When the Föhn blows, highs can reach 25 degrees, while sometimes, especially on early October, it can be colder, with highs about 10 degrees, hence already with an almost winter-like weather. You can check the weather forecast just before leaving, or you can bring spring/autumn clothes, with some warmer clothes (winter jacket, sweater), for evenings and colder days.

Munich, Marienplatz

The amount of sunshine in Munich is not high in autumn and winter months: the sun rarely shines from October to February, while it goes a bit better in summer: there are on average 7 hours of sunshine per day in June and August, and even 8 in July: for a German city, it's not little.

When to go

The best time to visit Munich 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, or a raincoat, which can be useful for sudden thunderstorms.