The growing deployment of wind and solar power in Europe makes electricity supply increasingly dependent on weather conditions. Ensuring security of supply during prolonged periods of low wind and solar generation, known as Dunkelflaute events, remains a key challenge. This thesis develops a detection framework to identify such events. The framework combines wind and solar capacity factors, weighted by installed capacity, and applies a variable mean-below-threshold algorithm to detect consecutive periods with weighted capacity factors below a given threshold. Multiple thresholds are used to capture both short, severe events and longer, moderate ones. Applying the detection framework to 40 years of historical weather data shows that Dunkelflaute events occur every year, though their severity and timing vary across regions and years.