Passage Summary: It hasn't rained all summer, and since it usually rains at least a little bit, the author assumes we are 'due' for a storm in the very last week.

Conclusion: It is likely to rain in the valley during the final week of the summer season.

Reasoning: Rain typically occurs every summer, and since no rain has fallen yet this year, it is expected to happen in the remaining time.

Analysis: This argument is a classic example of the Gambler's Fallacy. The author assumes that because a random event 'usually' happens within a timeframe, it becomes more likely to happen as that timeframe closes, simply because it hasn't happened yet. To match this flaw, look for an answer that claims an event is 'due' to occur based solely on a streak of it not occurring.