Let's put off the picnic until next week,when the weather may be better.when the weather may be better.一句是什么从句?什么从句，修饰什么？

Let's put off the picnic until next week,when the weather may be better.
when the weather may be better.一句是什么从句?
什么从句，修饰什么？

定语从句,修饰 next week

The wether may be better next week.