noun
during next week; sometime next week; throughout next week
Refers to an action or event taking place within the timeframe of next week. The exact interpretation (at some point vs. throughout) depends on context.
来週中にレポートを提出してください。
Please submit the report sometime next week.
来週中はずっと雨らしい。
It seems it will rain throughout next week.
Simply means 'next week' without the 'within/during' nuance.
Compound of 来週 (next week) + 中 (within/during).