Answer:
The sentence does contain an error concerning the punctuation of items in a series. The best option to correct it is:
b. A true baseball fan will go to a game in any kind of weather—on a chilly April day, during the heat and humidity of August, on a rainy September weekend, and even in temperatures dipping into the 30s.
Explanation:
Let's highlight the mistake in the original sentence:
"A true baseball fan will go to a game in any kind of weather—on a chilly April day, during the heat and humidity of August on a rainy September weekend, and even in temperatures dipping into the 30s."
There are two items that should be separated by a comma but are not. There is no punctuation whatsoever between them and, since they are long items, it gets confusing. Readers may think, at first, they are still reading about the humidity of August, taking a moment to realize the speaker is now talking of September. To correct it, all we have to do it add a comma between the items. That is exactly what option b does:
b. A true baseball fan will go to a game in any kind of weather—on a chilly April day, during the heat and humidity of August, on a rainy September weekend, and even in temperatures dipping into the 30s.
