How do you say

In the last three months, the weather in Beijing has been quite unstable.

..in Chinese?

过去三个月里,北京的天气变化非常大。

guò qù sān gè yuè lǐ , běi jīng de tiān qì biàn huà fēi cháng dà 。

How do you say "He works out for half an hour every day." in Chinese?