system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the wind whistle and howl when it's cold, but not when it's warm?
gpt
Two part answer:

1.  The wind does whistle and howl when it's warm also.  Go to a sailing club on a windy enough day, warm or cold, and you'll hear the whistling and howling in the masts and wire rigging. 

2. Cold air is more dense (heavy), so you get the whistling effect at a lower speed.  You might not hear the whistle until it's blowing 30 MPH if it's warm, while you may get it at only 20 MPH when it's cold.  Those aren't exact speeds, but reasonable examples.

As a sailor, the same temperature effect also applies.  A 20 MPH wind in the summertime is much easier to handle than a 20 MPH wind in the wintertime.  The same wind speed is hitting the sails, but the lower temperature literally makes the wind "heavy" and more powerful. There are more gas molecules per square inch per second.