Basics
Belgrade is located in central Serbia, at the crossroads of Europe, on the Paneuropean Corridor 10 and the Danube river, between the Panonian Plain in the north and the Balkan peninsula in the south.
Belgrade is located on three peninsulas formed by the Sava & Danube rivers, two of them relatively plain and the other one hilly (the largest part of the city). It’s average height is about 100 m above the MSL, while the highest peak, on mt. Avala, south of the city rises to 511 m. In the middle, on the Sava confluence lays the 2 km long Great War Island and a smaller one called Little War Island. There are about 10 more islands in the city, all uninhabited, the most important being Ada Ciganlija, aka. the Sea of Belgrade.
To the east of the city the hills grow over 300 meters above the mean sea level, while the Danube is about 80 m above the MSL. The northwest, from the Zemun district and through the Srem region Danube coast, there is a ridge that gradually grows into hills and then into the Fruška Gora massive.
Curiosity: In Belgrade’s metropolitan area, there are about 200 rivers & streams.
Surface
The city has an urban area of 360 square kilometres (140 sq mi), while together with its metropolitan area it covers 3,223 km2 (1,244 sq mi), divided into 17 municipalities.
Climate
The climate has been changing drastically during the last three years, displacing and shortening both the summer and the winter and making the spring and autumn pretty rainy. However, here are the official data from Wikipedia:
Belgrade’s climate exhibits influences of oceanic, humid continental and humid subtropical zones,[15] with four seasons and uniformly spread precipitation. Monthly averages range from 0.4 °C (32.7 °F) in January to 21.8 °C (71.2 °F) in July, with an annual mean of 12.2 °C (54.0 °F). There are, on average, 31 days a year when the temperature is above 30 °C, and 95 days when the temperature is above 25 °C. Belgrade receives about 680 millimetres (27 in) of precipitation a year, with late spring being wettest. The average annual number of sunny hours is 2,025. The sunniest months are July and August, with an average of about 10 sunny hours a day, while December and January are the gloomiest, with an average of 2–2.3 sunny hours a day.[16] The highest officially recorded temperature in Belgrade was +43.1 °C (110 °F) on 24 July 2007,[17] while on the other end, the lowest temperature was −26.2 °C (−15 °F) on 10 January 1893.[16]