Klagenfurt's winters are cold and unpredictable, with temperatures fluctuating between freezing lows and mild highs. January is the coldest month on average, with temperatures averaging around -5°C, while February can be even chillier, averaging just 0°C. Spring brings gradual warming, with March and April temperatures slowly rising to averages of 0°C and 2°C respectively. Summers are warm and pleasant, with June, July, and August all averaging highs above 15°C, with occasional heatwaves pushing temperatures into the mid-30s. Autumn is generally mild, with September and October temperatures ranging from cool to warm, before dropping again in November and December, which can be quite chilly, especially in January.