Right as rain...(assuming, of course, you used a primer intended for Al and prepared the surface properly, etc., etc, etc., ...).
Depending on the type of aluminum, a "standard" primer intended for housepaint may not work at all well. Would have to know far more than what you have said to have any hope of saying anything at all definitive other than it's somewhat surprising rain would have any really discernible effect if it was dry before the rain if it was indeed a suitable primer.
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