# Hottest core across every thermal zone and hwmon sensor lm-sensors knows
    # about. Reading the hottest rather than an average is deliberate: one core
    # throttling is a real problem that an average hides.
    local threshold={{ healthcheck_cpu_temp_threshold }}
    local hottest=0 label=""

    while read -r t; do
        [ -z "$t" ] && continue
        t=${t%.*}
        if [ "$t" -gt "$hottest" ]; then hottest=$t; fi
    done < <(sensors -u 2>/dev/null | awk '/_input:/ && /temp/ {print $2}')

    # Fall back to the kernel thermal zones if lm-sensors reports nothing.
    if [ "$hottest" -eq 0 ]; then
        for z in /sys/class/thermal/thermal_zone*/temp; do
            [ -r "$z" ] || continue
            local milli; milli=$(cat "$z" 2>/dev/null) || continue
            local c=$((milli / 1000))
            if [ "$c" -gt "$hottest" ]; then hottest=$c; label=$(cat "${z%/temp}/type" 2>/dev/null); fi
        done
    fi

    if [ "$hottest" -eq 0 ]; then
        MESSAGE="no temperature sensors readable"
        return 1
    fi
    MESSAGE="${hottest}C${label:+ (${label})}"
    [ "$hottest" -lt "$threshold" ]