Fly in rain only when the aircraft manufacturer permits it under the conditions you expect. A wind-resistance rating does not establish rain protection. Check the aircraft, battery and payload instructions. For example, DJI says the Mini 4 Pro is not waterproof.
Read the Aircraft Instructions First
Check the exact model and installed accessories before planning a wet-weather flight. An ingress-protection rating, where one exists, comes with conditions and limitations. Read those conditions on the manufacturer page and in the current manual. Do not transfer a rating from an enterprise aircraft to a consumer model. Also check the controller and payload instructions; a protected aircraft does not establish that every part of the system is suitable for rain. For the Mini 4 Pro, use the explicit waterproofing answer in the DJI FAQ when deciding whether the aircraft is suitable. DJI Mini 4 Pro waterproofing FAQ.
Check Rain Along the Route
Use the drone forecast precipitation field with nearby radar and local observations. A city forecast samples one location. A radar image gives a wider view of precipitation near the route. Check the image time and watch for movement toward the launch or landing area. Neither a dry forecast grid cell nor an old radar frame proves that the entire route will stay dry. Use a clear landing option if rain approaches. If conditions change before departure, repeat the check. The metro pages link to a nearby radar station so you can compare both views. VectorWX local forecasts and radar links.
Assess Visibility and the Landing Plan
Rain is only one part of the decision. Check the visibility, cloud clearance, wind and available landing area too. For Part 107 operations, use the visibility and cloud-separation requirements in section 107.51. A forecast ceiling does not show the horizontal distance to each cloud. Keep the aircraft instructions and the weather assessment together when deciding whether to depart. If water reaches the equipment, follow the manufacturer inspection and care procedure before another flight. Do not use a later dry forecast as evidence that wet equipment is ready. The preflight checklist helps you review these separate questions before you start the motors. 14 CFR 107.51 weather limitations.
Read Preflight Weather Checklist. Check current drone weather or the Chicago forecast before planning a local flight.