The territory of Trieste is composed of several different climate zones depending on the distance from the sea and elevation. The average temperatures are 5.7 °C (42 °F) in January and 24.1 °C (75 °F) in July. Climatic setting of the city closely resembles warm humid subtropical climate (Cfa according to Köppen climate classification) with some Mediterranean influences. On average, humidity levels are pleasantly low (~65%), while only two months (January & February) receive slightly less than 60 mm of precipitation. Trieste along with Istrian peninsula enjoys evenly distributed rainfall above 1,000 mm in total; it is noteworthy that no true summer drought occurs. Temperatures are very mild - lows below zero are very rare (with just 9 days per a year) and highs above 30°C similarly can be expected 15 days a year only. Winter maxima are lower than in typical Mediterranean zone (~ 5 - 11°C) with quite high minima (~2 - 8°C). Two basic weather patterns interchange - sunny, sometimes windy but often very cold days (max. +7, min. 0; frequently connected to an occurrence of northeast wind called Bora ) and rainy days with temperatures about 6 to 11 °C (43 to 52 °F). Absolute minimal temperature came with Arctic winter of 1956, -14.6°C. Summer is very warm with maxima about 28 degrees and lows above 20 degrees. Absolute maximum from 2003 is +37.2°C. Average year temperature, +15°C, is the same as Earth's average.
The year 2011 brought unusually dry conditions with 630 mm of precipitation and 54% humidity; the lowest temperature was -2.0°C and maximum was +33.8°C with average +15.9°C, higher than usual. Average speed of wind was 6.4 km/h, a very light wind when compared to other coastal cities of Mediterranean. Trieste is divided into 8a-10a zones according to USDA hardiness zoning; Villa Opicina (320 to 420 MSL) with 8a in upper suburban area down to 10a in especially shielded and windproof valleys close to the Adriatic sea.