It's still June, so the temperature goes down in the evening.
Once the rainy season is over, summer begins, and the temperature stays the same even at night.
この場合、次のような言い方ができます。
ーIt's still June, so the temperature goes down in the evening.
「まだ6月なので夜になると気温が下がる」
the temperature goes down で「気温が下がる」
ーOnce the rainy season is over, summer begins, and the temperature stays the same even at night.
「梅雨が終わると夏が始まり、夜でも気温は同じままです」＝「夜でも気温は下がらない」
rainy season「’梅雨」
ご参考まで！
It's still June so the temperature will drop at night.
"今はまだ6月なので夜になると気温が下がる"
- It's still June so the temperature will drop at night.
- It's June so it will get cooler when night comes.
今はまだ6月なので、夜になると気温が下がって過ごしやすいです。だけど梅雨が終わって夏が来ると、夜でも気温が下がりません。
- It's still June so the temperature will drop at night and it's easy to get by. However, after the rainy season ends and summer comes, the temperature will continue to stay the same at night.
カナダ 
アメリカ合衆国 
