Facial eczema spore counts are already at danger level for lambs in Turakina and Fordell - and could leap skyward after rain in these hot conditions.
There was about 10mm of rain in Turakina and Fordell on January 24, and facial eczema spore counts lifted to 30,000 there. Spore counts are a danger to lambs when they are more than 20,000.
Wanganui Veterinary Services had been doing spore counts for two weeks, general manager Tom Dinwiddie said.
Since the rain, conditions have been hot and dry, which kills the spores. But their levels could rise quickly if there is more rain, which MetService predicts for Friday.
If that happened, and the weather continued to be hot and still, farmers should be ready to act quickly to protect their stock, Dinwiddie said.