Tenrankoku no Sora Yomishi: Isekai de Tenkiyohou Hajimemasu.

Hazuki is a weather forecaster who finds herself in a Chinese-style parallel world. While selling umbrellas in the city, she receives a request from an official to predict the weather for the Vernal Equinox Festival. She rashly agrees, but if she fails, she'll be beheaded... Who knew!?

(Source: Kadokawa, translated)