What wind speeds cause flights to be delayed or cancelled?

[PuttingOutFirewithGasoline]

Just panicking a bit about flight, looks like wind of up to 50 50mph??

It's more complicated than that.

If the wind is across the runway that's a problem. If it's along, not so much.

If the wind is stable and in the "right" direction, then 50mph is not going to cause too much trouble.

Thank you

I'm flying tomorrow and had the same wondering.

As other posters said, it's a lot more complex than just speed. The biggest factor is the direction of the wind VS the runway direction. Planes take off and land into the wind so if the directions match, there's no issue. If the wind is across the runway, that's when it gets a bit tasty. Each plane (and operator) will have a crosswind limit ie what is safe for that type of plane. That cannot be exceeded and the plane will either not attempt a landing, or may divert after trying. That being said, any wind speed/direction can cause issues should windsheer appear. Look at the wind direction/gust speed and compare to the runway you're going to be on!

Oh lord that sounds complicated. Also doesn't wind move direction?

Wind can move direction yes.

If it is changing so much and so quickly that there is a significant risk the take offs and landings are delayed.

Hence the "waiting for slot".

The airport can measure wind speed and direction in real time.

Some airports have more than one runway, and they face in different directions, so they can use whichever one is most suitable on the day. In the UK, I think generally the prevailing winds are either from the south-west, or from the north-east, so many runways run SW-NE and they can take off or land from either end.

As a pp says, it is cross-winds blowing sideways across the runway which can cause issues. 50mph isn't too much of an issue though.