What is defined as the difference between the hottest and coldest months measured by monthly mean temperatures?

The concept being described is known as the annual temperature range. This refers specifically to the fluctuation in temperature across the year, measured by the difference between the average temperatures of the warmest month and the coldest month. This range provides insight into the climate characteristics of a given region, indicating how extreme or moderate the seasonal variations are.

For instance, a region with a high annual temperature range would experience significant temperature fluctuations, which could suggest a temperate climate with distinct seasons. In contrast, a region with a low annual temperature range would generally have a more stable, consistent climate, possibly indicative of tropical conditions where temperatures remain fairly constant throughout the year.

The other options do not accurately encapsulate the specific temperature differentiation described in the question. Climate variability pertains to variations in climate patterns over time, seasonal temperature shift refers to changes in temperatures as seasons transition, and average temperature does not involve the comparison between the extremes of hot and cold months specifically. Thus, the definition aligning with the difference between the hottest and coldest months, as described, is indeed the annual temperature range.