The Spring into Summer Extravaganza was due to take place at Springfield Park in Kidderminster on Saturday.
However, organisers decided to call off the free event as it was setting up, due to heavy rain and the forecast of more poor weather to come.
The free event was set to feature a range of activities, including a bouncy castle and face painting, as well as a performance from the Black Country Beatles.
The fun day was part of a weekend of events being held in the Horsefair area.
The official opening of the Horsefair clock on Saturday at 4.30pm and the Mr Tee in the Park event at St George’s Park on Sunday, August 22 were still scheduled to go ahead.