じょうじゅん上旬joujun
1.
The period encompassing the first ten days of a given month, typically referred to as early in the month.
2.
A time frame that signifies the initial phase of a month, specifically from the 1st to the 10th day, often associated with the start of various monthly activities or cycles.
3.
The segment of a month that includes the first ten days, marking the beginning of monthly events or schedules, and distinguished from the middle and latter parts of the month.
Example:
７月の上旬は、海に行くのは早いかな？