MatthiasWindZone.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class MatthiasWindZone : MonoBehaviour {

    List<Rigidbody> RigidbodiesInWindZoneList = new List<Rigidbody>();
    public Vector3 windDirection = Vector3.right;
    public float windStrength = 5;

    private void OnTriggerEnter(Collider col)
    {
        Rigidbody objectRigid = col.gameObject.GetComponent<Rigidbody>();
        if(objectRigid != null)
            RigidbodiesInWindZoneList.Add(objectRigid);
    }

    private void OnTriggerExit(Collider col)
    {
        Rigidbody objectRigid = col.gameObject.GetComponent<Rigidbody>();
		if (objectRigid != null)
			RigidbodiesInWindZoneList.Remove(objectRigid);
    }

    private void FixedUpdate()
    {
        if(RigidbodiesInWindZoneList.Count > 0) {
            foreach (Rigidbody rigid in RigidbodiesInWindZoneList)
            {
                rigid.AddForce(windDirection * windStrength);
            }
        }
    }
}