Can I still send her a short message about the weather forecast after breaking up?

No, since she doesn't love you anymore, she won't look back unless she still loves you. Anyway, you have the habit of sending weather forecasts in groups, so keep sending them to her. Maybe she will turn back, but I don't think there is much hope. Just try it. You're used to it anyway. Even if we are not together, we will not regret it. Come on! I hope you can be together.