First Ten Days Of The Month
Beginning Of Month, Beginning Of The Month
noun
The above time of the month Is the top part of the month. The first ten days of the month, or the beginning of the month.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
気象庁は六月上旬に梅雨が始まると言っている。
The Japan Meteorological Agency says the rainy season will start at the beginning of June.