"It’s the height of the season"?

The question is from the transcript of a podcast:

Mmmm, blueberries. It’s the height of the season, and I’ve been tossing a handful onto cereal, into pancakes or just straight into my mouth.

I don't understand what does the sentence "It's the height of the season" mean.

• What does "it" refer to? Does it indicate "blueberries"?
• What does "the height of the season" mean?

Solution 1:

The season is the yearly period in which a certain activity is best performed for whatever reason, usually something that depends on climate and natural seasons. Cf. the hunting season, the asparagus season. The blueberry season is when blueberries are ripe for the picking.

The height of the season is the very best point within this period to pick blueberries, probably because there are the most, or they taste best.

It is more or less a dummy subject; you could say it means "this time", just as in it is sunny in London.

Solution 2:

"Now is the height of the blueberry season, when they are common and tasty."

(actually the season's nearly over by now: go and pick blueberries, rather than surfing the net).