Why is it easier to wash bloodied clothes with cold water?

[Syzygys]

Maybe warm water helps the still not completely dry blood to stick to the surface? Also how does the salt help the cause? (red wine on a dinner tablecloth)

Edit: google says hot water will set the stain. Well, I knew that, what I want to know what exactly happens chemically that makes setting easier with warm water?

[S.A.M.]

Because heat hardens proteins [denaturation] and makes them less soluble?

[Fraggle Rocker]

Because heat hardens proteins [denaturation] and makes them less soluble?

Exactly. Drop an egg on your shirt and let it soak in. You can probably get it out with some energetic hand-washing. But put the shirt in the microwave and cook the egg protein, and getting it clean will be a real project.