Teacher: In this task, you're given passages that contain mentions of a time duration related quesry and we are supposed to write answer to a question that involves event “frequency", which refers to how often an event is likely to be repeated. For example, "taking showers" typically occurs ~5 times a week, "going to saturday market" usually happens every few weeks/months, etc. 
 Note that a lot of the questions could have more than one correct answers. We only need a single most-likely answer. Please try to keep your "answer" as simple as possible. Concise and simple "answer" is preferred over those complex and verbose ones.  
Teacher: Now, understand the problem? If you are still confused, see the following example:
Sentence: Namibia conducts a census every ten years. After independence the first Population and Housing Census was carried out in 1991, further rounds followed in 2001 and 2011. The data collection method is to count every person resident in Namibia on the census reference night, wherever they happen to be. This is called the de facto method. For enumeration purposes the country is demarcated into 4,042 enumeration areas. These areas do not overlap with constituency boundaries to get reliable data for election purposes as well. 
Question: How often does Namibia conduct a census?
Solution: every ten years
Reason: Census is generally conducted every ten years in most countries like Namibia.

Now, solve this instance: Sentence: The climate of the coastal plain is influenced by the Atlantic Ocean, which keeps conditions mild in winter and moderate, although humid, in summer. The highest coastal, daytime temperature averages less than 89 °F (32 °C) during summer months. The coast has mild temperatures in winter, with daytime highs rarely below 40 °F (4 °C). The average daytime temperature in the coastal plain is usually in the mid-50s °F (11–14 °C) in winter. Temperatures in the coastal plain only occasionally drop below the freezing point at night. The coastal plain averages only around 1 inch (2.5 cm) of snow or ice annually, and in many years, there may be no snow or ice at all. 
Question: How often do temperatures on the coastal plain of NC drop below freezing at night?
Student:
occasionally