event temperature { has $value, $area }
event humidity    { has $value, $area }
event fire-risk {
    my temperature #temp;
    my temperature #temp2;

    has $temperature = #temp.value;
    has $humidity    = #hum.value;
    match {
        [
            temperature(#temp, value > 40, ?area == #hum.area )
            &
            humidity(#hum, value < 20, ?area == #temp.area)
        ] 5min
    }
}