How long does it take most builders to build your average suburban 2 story home? how depends?

is it likely the builder was telling my brother in law the truth that it would take about 4 months for him to build it? it is your average sized middle class suburban home that would find in a "Cookie cutter style neighborhood"

ALSO WHY MANY START BUILDING ONLY WHEN IT IS VERY DRY IN AUGUST?
Update: I WAS THINKING IT SOUNDED LIKE A UNREALISTIC TIME ESTIMATE...DONT THEY USUALLY TAKE LIKE 6 - 9 MONTHS TO BUILD?
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