The iPhone’s moisture detection mechanism is very sensitive and can be triggered by the slightest bit of moisture or even condensation in the port or on the charging cable.
Evgen_Prozhyrko/Getty ImagesiPhones have a lot of built-in mechanisms to help prevent you from damaging the battery or the phone. For example, if your iPhone is too hot, it will stop charging. But did you know that it also stops charging when it detects water in the charging port?
Here’s the message that’s displayed when you try to charge an iPhone with moisture in the charge port.

“Liquid Detected in Lightning Connector” message in the iPhone
Adrian Kingsley-Hughes/ZDNETNotice how it offers two options.
One is Dismiss, which, as the wording suggests, dismisses the warning, and disables the charging process until the next time the charging cable is connected.
Also: Phone overheating? Here are 8 potential causes and their solutions
The other is Emergency Override. Pressing this overrides the warning and instructs the iPhone to proceed with charging.
Which should you choose?
Ideally, if you get this message, you should do what the iPhone suggests, and disconnect the charge lead and allow the port to dry. Blowing a fan or a hair dryer on a low, cold setting will help speed up the process.
However, the iPhone’s moisture detection mechanism is very sensitive and can be triggered by the slightest bit of moisture or even condensation in the port or on the charging cable. If there’s no visible water in the port, I have –at times of real need — cleaned the connector with a dry cloth, plugged it back in, and then used Emergency Override to charge up the iPhone.

I keep an eye on the handset, unplug and replug in the charging cable after a few minutes, and usually, the charging process has dried off the charge port completely, and the next time it charges normally.
Also: The best wireless chargers for iPhone and Android phones
While this has always worked for me, be aware that there are risks. An alternative would be to use wireless charging until the port dries out.  

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https://www.zdnet.com/article/water-in-your-iphones-charging-port-should-you-use-the-emergency-override/