Cold
Is it eaten with wasabi and ginger?
Udon
 "Zaru udon": Chilled udon noodles topped with shredded nori and served on a zaru (笊 or ざる), a sieve-like bamboo tray. Accompanied by a chilled dipping sauce, usually a strong mixture of dashi, mirin, and shoyu. Eaten with wasabi or grated ginger.  "Bukkake udon": Cold udon served with thick dashi-broth.  "Hadaka udon" (naked udon 裸うどん): Cold udon served on its own.  Kijoyu udon: Served in a cold soup of raw (unpasteurized) soy sauce and sudachi (a type of citrus) juice, sometimes with a bit of grated daikon.