Why was the "first Monday in December" originally chosen as the default meeting date for Congress?

Question

The original Constitution of the United States did not explicitly specify many dates, but one was the default date for which Congress was required to meet:

The Congress shall assemble at least once in every Year, and such Meeting shall be on the first Monday in December, unless they shall by Law appoint a different Day.

Article I, Section 4, Clause 2

Why was this particular original date chosen?

Note that Clause 1 of the same section left the date of Congressional elections to be determined by state and federal laws, rather than an explicit date written into the Constitution (see this question). In turn, the date that was eventually chosen for these elections then influenced the writing of the 20th Amendment, which set a new default date for Congress to assemble (January 3rd). But how was the original date chosen?

Answer 1

According to senate.gov

When should Congress begin its annual session? The 18th-century framers of the United States Constitution, accustomed to an agriculturally based economy with its cycles of planting, growing, and harvesting, considered the mostly dormant month of December to be a particularly good time for senators and representatives to begin their legislative sessions.