The Maitland Valley Conservation Authority recorded 125 mm of rain in the Wingham area on Wednesday.
The authority released a watershed condition statement Thursday morning.
Severe thunderstorms tracked through the region yesterday and brought significant rainfall to localized areas within the Maitland and Nine Mile River watersheds.
The 24-hour rainfall totals ranged from 30 to 125 mm, with heaviest amounts generally concentrated in a wide corridor extending from Goderich to Howick.
The MVCA says significant flooding is not expected but river levels will rise throughout the day, especially along the Lower Maitland downstream of Wingham.
Campers and anyone participating in recreational activities within river lowlands are advised to use caution and be aware of the potential for fast changing conditions.