An unusually hot and humid summer in the North Island has stained wool yellow, making it harder to sell and leading to lower prices.
Hawke's Bay wool broker Philippa Wright says some North Island farmers aren't affected, but overall there is a big difference in wool colour this year.
The cross-bred wool market has struggled for the past 18 months, after its key market in China started favouring finer fibre fashions.
Traditionally wool did deteriorate in colour during summer, but Ms Wright said the hot humid and wet weather was worst for North Island wool growers, particularly in her region.
"We've got quite a dramatic drop in our wool colour range. It normally only affects the longer wools but we're seeing it right through to the lambs second shear.
"There's nothing anyone can do about that, it's just a climatical condition."
Hawke's Bay wool is well known for its high 'Y' value and good colour that washes and dyes well, she said.
But the weather had changed it to a yellow-toned wool.
"So it limits the ability for dyeing and where it can go, it takes it from a B styled wool to a BC often.
"There's a detrimental affect to farmers, it certainly makes a difference to the price, and with the price being so low at the moment."
The yellow wool was also tougher to sell.
"So all of a sudden instead of having a large majority of white wool, we've got wool of a poorer colour. So we have to find a home for that.
"That definitely does make it harder and it slows the process down. It means there's a whole lot more wool in that lower grade as opposed to the top."
She said one upside to the humid weather was that the grass growth had been much better than previous summers.