As a Hawaii based commercial drone pilot I am regularly asked to fly drones in relatively high wind. Here on Maui we typically get winds in the 20 knot range with gusts into the 30's and sometimes 40's. Whenever I am assigned an aerial media capture task in wind I have to make an assessment and determine if it is safe enough to fly without losing a drone, flying out of control, or hurting someone. Obviously a “no fly” call is not ideal and usually means an immediate financial loss in the fast paced world of commercial drone services. Many times this high wind flying occurs over water (shark infested salt water to be exact!) which increases the risk and complexity of the operation. Also, as you may know losing a drone into the big blue sea kind of negates your ability to get a replacement via insurance such as DJI Care Refresh unless you can retrieve the drone to send it back to DJI. The good news is you usually don't encounter obstacles over water and image transmission is rarely interrupted due to object interference. The challenge is that if you have a problem you need to first traverse a considerable distance over No Man's Land before you even have a chance of retrieving your drone.
To prepare for a scheduled drone shoot of, say kitesurfing for instance, I do several things. First I check to see if the location I'm going to be flying at is a “green zone”. This means it is not in an FAA no fly zone, not within 5 miles of an airport, and has a legal launch and land area within visual sight distance of the drone's area of operations. Next I take care of the insurance, permits, and any necessary FAA clearances required to do the job. Once the location is approved I check the local weather, do a pre-shoot site survey, and draw up a plan for shooting as well as a plan for emergencies based on prevailing wind direction and coastline topography. Finally I book my assistant for the shoot as a visual spotter is required by law and is highly recommended when pushing the limits of a drone's flying capabilities.
What I'm looking for when I check the weather is if there is going to be sun (drone shots need sun) and how strong the wind will be. Also the gust factor of the wind is a biggie. A lot of variability in the wind really degrades the flying experience and can cause the drone to pitch and roll a lot more than steady wind. Depending on the wind speed I determine if my drone can handle the upper limits of the wind prediction. Direction is key as well. Offshore winds present a far greater risk than Onshore winds when flying over water for obvious reasons. And finally I consider the conditions when determining not only if I can fly but also how close, what is the subject doing, what are any other obstacles, what is my drone's range, and what is a safe altitude. With kitesurfing you have a fast moving kite at the end of 30 meter lines so any shots lower than 100 feet need to account for this action and associated risk.
On shoot day you want to assess the actual wind and weather conditions (don't get caught by rain), and make the final determination to fly or not to fly. I like to do this prior to clients or other aspects of production showing up so I can make the decision without biased influence. If it is a “go” situation I fly my drone in normal GPS mode up to about 10 feet and see if it can stay in place. If it is really windy in your launch area don't launch from the ground or your drone can flip over before it takes off. If you're able to hover in place without losing ground try flying up to your maximum shoot altitude and test the wind speed there. If the wind starts to overtake your drone and it drifts away bring it back down to a lower altitude and try to recover it. If it is too windy to recover your drone in GPS mode you can try switching to “sport mode” (DJI Mavic Pro and Phantom 4 series) and fly it back to you. Make sure you are familiar with switching to and flying in sport mode prior to flight. While your drone is drifting away is not a good time to go through the set-up menu for the first time. If sport mode is not an option and there are obstacles around you can use these as windbreakers. If you are flying the drone back towards yourself at full speed and the wind is still overpowering the drone you can dip behind buildings, trees, barriers, and even mountains to get into a more stable environment. Although obstacles can increase wind variability I have found a combination of lowering your altitude and getting behind things that slow down the wind can get you out of most situations and at least allow you to get the drone down to the ground and not in the water. If the wind is blowing away from shore and out to sea you have few options for recovery and the wind may be just as strong 10 feet off the water as it is 100 feet up. Strong and (typically) gusty offshore winds present the highest risk of losing your drone over water and should be approached with an added level of consideration.
In conclusion just remember to be safe, not sorry. Don't push your drone into an unrecoverable situation and have several backup plans in mind for possible emergencies. Know your equipment well before flying in wind or over water including time and distance limits as well as the effects of wind on relative speed vs surface speed. For instance if your drone flies 25 Mph top speed and it is gusting 15 to 20 Mph it may fly downwind at a surface speed of 45 Mph but may only be able to go upwind at 5 Mph. If your drone flew a mile downwind make sure you have enough battery to make it back upwind at 5 Mph, which by my calculations would take roughly 12 minutes. Also “sport mode” increases speed but decreases battery life. And finally try to avoid flying your drone on empty. Flying performance can be less than expected when the battery gets low and it definitely increases the stress level when you're down in the single digits and not yet back to shore.