If it gets cold in your garage - like 32F+ - then it is cold enough. Here in this zone 9 our 'worst' frost would be around -7C and each of the species you've listed winters over and flowers the following spring. We have only a few mornings with frost and the ice is usually all melted and gone before noon.

If you do put them in a 'warmer' place - make sure they are well-watered over the winter so they continue to increase their roots - and get light when the leaves start to show above ground. (If you don't they end up looking like scallions...)

Could I just leave them in the urns outside? If so, would I need to water them during the winter?

I would think you SHOULD leave them outside in the winter. You say the urns are large, so plant the bulbs toward the center of the pot if you're afraid they will freeze. But most bulbs need that winter chill to trigger them to bloom in the spring. (Hyacinths and tulips actually need to be chilled in the fridge for 6 to 8 weeks to bloom here.) You should water them through the winter if you don't get rain. Most years, we get enough rain that I don't have to water my bulb pots. Stick your finger in the soil once in awhile. If it's dry, water.
Your urns will look more attractive throughout the winter if you can plant some cool season annuals in them too: pansies, snapdragons, forget me nots, lobelia are all good here. Check around for what works in your area (if any).

It depends how large the urns are. I tried those plastic square pots Walmart sells one year, the bulbs all rotted. But I'm further north. My garage isn't insulated, potted bulbs do great in there.

Which direction does this garage face? In the midwest, you get forceful drying winds, in winter. You'll want to water those pots often enough to keep the wind from dessicating the contents, if the spot they are in is exposed. If the garage doors are on the leeward side of the garage, you won't need to water as often.

You drive to & from the garage every day--just touch the soil & look at it & see how it is doing. Also you could lay down some mulch for the winter to protect from drying--after frost, cut some newspapers to fit the pots, hold it down with a thin layer of almost anything---some gravel, regular mulch, etc. You're the only one who will see it up close.