My orange 38 litre rubbermmaid eventually cracked on the inside so waaas just a wasted vessel.
1 Large insulated vessel
2/ Pond pump
3/ Unused useless plate chiller
4/ Immersion chiller
Set up the pond pump in the rubbermaid so that the cooled water can circulate through the plate chiller and back into the rubbermaid
Fill the insulated vessel with water to about 3/4 full and at about 30 minutes from the end of boil add 12 frozen pet bottles of a Belgian beer you brewed 10 years ago and never drunk.
At flame out use your immersion chiller to get the wort down as low as possible using tap water. Then connect the brew kettle to the plate chiller and allow the kettle to run out under gravity while the pond pump passes the cold water through the other side of the plate chiller.
Even on the hottest day you should get to pitching temperature. A bag of ice would further help.
Or you could no chill until the weather is cooler.

Steve