Hennef's winter months, January and February, are quite chilly with temperatures often below freezing, averaging around 0-3°C. As the seasons transition into spring, March and April bring mild temperatures, occasionally reaching up to 22°C, but still averaging around 5°C. Summer months, June and July, experience warmer days, sometimes even reaching as high as 29°C in June, while August's temperature averages slightly lower at around 15°C. Autumn brings a gradual drop in temperature, with September being relatively warm, averaging 15°C, before cooling down to around 9°C by October. Winters return in December and November, with temperatures mirroring those of January and February.