What you're seeing is a built-in battery protection feature, not a fault. Since iOS 16, when the iPhone gets too hot — or too cold — it automatically pauses charging and shows a 'Charging On Hold' message on the lock screen and in Settings → Battery. Charging resumes on its own once the temperature is back in the normal range.
Heat is the main factor that ages batteries prematurely, and charging itself generates heat, so the pause protects long-term battery health as well as preventing immediate damage. Apple's recommended charging range is 0–35 °C; sustained heat above that can permanently shorten battery life.
To charge comfortably in warm weather: remove thick cases, keep the phone out of direct sunlight and hot cars, prefer a slow charger when you don't need speed, and avoid heavy use while charging.
If pauses happen regularly in a cool room with the original charger, the battery itself may be worth a check — but occasional summer pauses are completely normal.
Sources: https://support.apple.com/104949 · https://support.apple.com/guide/iphone/iph3006fbee4/ios
— Osnivo Editorial