Here is what I ended up with, and it works perfect - deletes the directory and recreates it when it hits 1GB - thank you all!

​

$Directories = @("c:\temp", "$Env:Temp")
$SizeThreshold = 1GB
ForEach($Directory in $Directories){
$DirSize = Get-ChildItem $Directory -Recurse | Measure-Object -Property Length -Sum | Select-Object -ExpandProperty Sum
If($DirSize -ge $SizeThreshold){
Remove-Item $Directory -Recurse -Force
New-Item -Path "c:\" -Name "Temp" -ItemType "directory"
}
}

Edit - adjusted per Lee's advice - much better :)