How is prevailing visibility described if the observed visibility is noted as varying between three to five miles?

When prevailing visibility is determined based on varying observed visibility, it is recorded as the most common distance observed during a specific observation period. In this case, if the visibility is noted to be varying between three to five miles, the amount of visibility that occurs most frequently would need to be identified. Since the range is from three to five miles, the midpoint is typically considered, which in this case would be four miles.

When reporting visibility, it is common practice to round to the nearest whole mile if necessary, and as such, four miles is the value that best represents the prevailing visibility within that range. Factors like duration and frequency of visibility at certain distances also influence this determination, but the average or commonly experienced distance is what's pertinent. Thus, four statute miles serves as the appropriate recorded visibility in this scenario.