also: なつき
noun
summer season; summer; summertime
Refers to the summer season as a period of the year, often used in formal or written contexts. Compare with 夏 (なつ), which is the everyday word for summer.
夏季休暇は来月から始まります。
The summer vacation starts next month.
この地域の夏季の平均
The average summer temperature in this region exceeds 30 degrees.
夏 is the common, everyday word for summer. 夏季 is more formal and often used in written language, schedules, or official contexts.
Compound of 夏 (summer) and 季 (season). The reading かき is the on'yomi, while なつき is a rare kun'yomi-based reading.