no way for moisture to get into the new connection. Before connecting, slip some shrink wrap over one of the wires. Solder then before covering with shrink wrap apply some silicone grease - autozone has little packets they call bulb grease (I just use tub of synthetic grease). Slide over the shrink wrap and shrink to fit. All will be well sealed from moisture. Used this technique many time over the years for fog lamp and other installs on a variety of vehicles.
Somewhere here I have an autoFAQ giving that advice —believe it was for injector connector rewiring.