Complex sentence: In mainland Europe, early snowfall was seen across much of the western half of the continent on 17 December, when the Swiss canton of Grisons saw a record-low overnight temperature of − 32 ° C (− 25.6 ° F).
Split into simpler sentences: In mainland Europe, early snowfall was seen across much of the western half of the continent. On 17 December, the Swiss canton of Grisons saw a record-low overnight temperature of − 32 ° C (− 25.6 ° F).