First you need to define the unit for your metrics (perfdata) in a metrics definition file or change the name of your metric to a predefined value. You could try humidity
and ‘temp’ as metric name. This will match this predefined metrics:
metric_info["humidity"] = {
"title": _("Relative humidity"),
"unit": "%",
"color": "#90b0b0",
}
metric_info["temp"] = {
"title": _("Temperature"),
"unit": "c",
"color": "16/a",
}
Second, as far as I know you can not have two metrics wit different units in one graph, so you will have two graphs.