I go to UAVForcast.com before I fly to check the wind speed at 300 feet, which is my typical altitude (there are many trees here). I set the maximum at 15 mph. Am I too cautious? What should the maximum safe wind speed be?
You can fly in higher winds (20-25) but you just need to be comfortable AND you need to know how to fly in ATTI mode. Plus you need to make sure you always fly upwind, that way if your battery gets low you will always come home faster since your gong with the wind.
And learn in ATTI in case you lose GPS and the aircraft will then drift in the wind.
All it means is the aircraft is not using the GPS to hold it's horizontal position.
It will drift in the wind but it's orientation will still stay level and it will stay at the same altitude.
One day you will be flying and it will lose GPS and go into ATTI and then you will need to take over and fly it.
If you can only fly in GPS mode (letting go of the sticks and it holds position) then you may panic.
Many many crashes have happened because they lost GPS signal for whatever reason (between buildings or something else) and it went into ATTI and they do not know how to fly the aircraft in that mode.
I routinely fly in winds as high as 25 mph. I don't like it, but I have no choice around here. I fly cross wind, and up wind. but not down wind very far. Maybe a hundred or two hundred yards at most. I always manually take off and get up to at least 10 feet fast. The auto take off feature will let the drone drift downwind just a little until it get stabilized. I always use the manual landings too. I fly both the P3S and my new P3P. Both are very stable in winds. They work hard to hold position, but they do it. Practice make perfect.
The first time I tried flying in strong winds, I lost control and the thing went down wind about 300 yards. I could not figure out which way it was pointing to bring it back. All of my control inputs just made it go farther away. I panicked and hit the RTH button. The darn thing took control and came home as pretty as you please. Then landed right in front of me. At the time it never occurred to me to look at the blue triangle on the map to see which way it was pointing. Live and learn!
At some point a useful trick to learn is flying back home without using the GPS; it is in fact quite simple to learn. As long as you can see your phantom (tiny speck is OK) this works. Give your craft some forward throttle. If you observe the craft moving rightwards, give some right rudder. If you see it moving leftwards give it left rudder. Do this alternatively as the craft reduces its left-right movements and you'll see it coming straight to you. Practice this the first few times without wind in a large field. You'll soon be comfortable with the method and can try it when your craft is far out.
Have fun & good flying (upwind)... and take care of those landings on windy days!