No weather machine. I just found them in my inventory after the architect home was built.
If game is working correctly, weather related pool items placed at a lot go into inventory automatically if you place a weather machine and weather is changed. I think the only winter item is hockey nets. Summer items are water volley ball net, pool cleaner, floating chairs/rings, and riding animals. When weather changes back, they go back to their former place, as long as they haven't been removed from inventory and placed elsewhere.
So if the architect home preview is summer (blue skies on weather machine), as is seems to always be, you wouldn't know if hockey nets were there even when you built a home with a pool unless you placed a weather machine and set it to winter (snow on weather machine) or looked in your pool items in inventory.
Hope this is clear.