毎年、私たちの町は春には暖かい天気になる。

、。

Every year, our town gets warm weather in spring.

Literal

Every-year, our town [topic-は] spring [in-には] warm weather [into-に] becomes.

暖かい天気になる ('becomes warm weather') — another になる state change. 春には ('in spring, as for spring') uses the contrastive は with the temporal に for mild emphasis on spring specifically.