Is my hair dirty enough to dye it?

I'm asking because I bought blonde dye, but I took a shower last night and I don't know if my hair is dirty enough. I know your hair has to be dirty so that the dye stays locked in and won't just slide of the strands. If i took my shower around 9:30 last night, and since then i've slept, straightened my hair, and gone sledding would it be dirty enough?