What is a key characteristic of Calistoga's summer temperatures?

The correct choice highlights that Calistoga's summer temperatures peak at around 90 degrees, which reflects the region's climate accurately. Calistoga, located in Napa Valley, experiences warm to hot summer weather characterized by dry conditions and plenty of sunshine. This seasonal warmth supports the growth of various grape varieties, influencing the area's renowned wine production.

Understanding the context of the other options clarifies why they do not fit. The statement about temperatures rarely exceeding 80 degrees underestimates the actual summer highs typical for this region, while the idea that temperatures are moderate all summer does not account for the pronounced warmth experienced during peak summer months. Lastly, the suggestion of consistent humidity is misleading, as Calistoga tends to be rather dry, especially compared to other regions where humidity plays a significant role in the climate. The peak temperatures around 90 degrees are therefore a defining feature of Calistoga's summer weather, shaping both its climate and agricultural landscape.