When walking in the rain, a gentleman walks on the side of the street so that he would be the one who gets wet if a car splashes onto the curb.
If there is a possibility of rain, bring 2 umbrellas. Sharing an umbrella generally brings two people in ‘too close for Halacha’ proximity.
Plan accordingly to minimize the time outside in the rain. If it is raining, plan to go someplace where the parking lot is very close to the destination. If when you come to the destination, and you realize it is too noisy or not conducive to good conversation, don’t just say “it’s too noisy here, let’s go somewhere else…’. Ask her what she prefers. Many women really don’t like to walk in the rain.