RSPCA officers have examined 43 horses stranded in flooded fields where three animals died in the wake of the storms.
Conservative MP Peter Bone raised concerns last week about some 100 horses that graze in fields along the Embankment in Wellingborough.
The charity said it was monitoring the site in Northamptonshire and had inspected the animals on Wednesday.
It found five horses were in a poor condition. The ownership of both the land and the horses is unclear.
Bad weather, including Storms Ciara and Dennis, have flooded the fields, limiting the animals' shelter and food.
An RSPCA spokeswoman said it had visited the field along with representatives of World Horse Welfare, which provided hay for the horses, and Wellingborough Borough Council.
She said: "We now plan to return to the site at the earliest opportunity with other agencies to carry out a detailed veterinary examination on all the horses.
"This will be carried out once we have made arrangements with the staff and vets needed to carry out this task and also for accommodation, should some of the horses need to be taken away for treatment. In the meantime we will monitor the site on a daily basis."