Here is a very simple script which can help you to monitor average load on Linux system.

Shows immediate value, max, min and average over monitoring for all 1 minute, 5 minutes and 15 minutes load. It runs in infinite loop you need to cancel it with CTRL+C.

#!/bin/bash

## here you can set num of seconds between checks
SLEEPSEC=5
##

unset arr1min
unset arr5min
unset arr15min
CYCLES=0
MAX1MIN=0
MAX5MIN=0
MAX15MIN=0
CPUNUM=$(grep processor /proc/cpuinfo|wc -l)
MIN5MIN=$CPUNUM
MIN1MIN=$CPUNUM
MIN15MIN=$CPUNUM

while true
do
	TIMESTAMP=$(date +"%Y-%m-%d %H:%M:%S") 
	CYCLES=$(( $CYCLES+1 ))
	LOAD1MIN=$(cat /proc/loadavg|cut -d' ' -f1)
	LOAD5MIN=$(cat /proc/loadavg|cut -d' ' -f2)
	LOAD15MIN=$(cat /proc/loadavg|cut -d' ' -f3)

	arr1min[$CYCLES]=$LOAD1MIN
	arr5min[$CYCLES]=$LOAD5MIN
	arr15min[$CYCLES]=$LOAD15MIN

	SUM1MIN=0
	SUM5MIN=0
	SUM15MIN=0
	for ((i=1;i<CYCLES;i++)) do SUM1MIN=$(echo "$SUM1MIN+${arr1min[$i]}"|bc ) SUM5MIN=$(echo "$SUM5MIN+${arr5min[$i]}"|bc ) SUM15MIN=$(echo "$SUM15MIN+${arr15min[$i]}"|bc ) done AVG1MIN=$(echo "scale=4; $SUM1MIN/$CYCLES"|bc ) AVG5MIN=$(echo "scale=4; $SUM5MIN/$CYCLES"|bc ) AVG15MIN=$(echo "scale=4; $SUM15MIN/$CYCLES"|bc ) ## 1 min if [ $( echo "$LOAD1MIN > $MAX1MIN"|bc ) -eq 1 ]
	then
		MAX1MIN=$LOAD1MIN
		MAX1MINTIME=$TIMESTAMP
	fi
	
	if [ $( echo "$LOAD1MIN < $MIN1MIN"|bc ) -eq 1 ] then MIN1MIN=$LOAD1MIN MIN1MINTIME=$TIMESTAMP fi ## 5 min if [ $( echo "$LOAD5MIN > $MAX5MIN"|bc ) -eq 1 ]
        then
                MAX5MIN=$LOAD5MIN
                MAX5MINTIME=$TIMESTAMP
        fi

        if [ $( echo "$LOAD5MIN < $MIN5MIN"|bc ) -eq 1 ] then MIN5MIN=$LOAD5MIN MIN5MINTIME=$TIMESTAMP fi ## 15 min if [ $( echo "$LOAD15MIN > $MAX15MIN"|bc ) -eq 1 ]
        then
                MAX15MIN=$LOAD15MIN
                MAX15MINTIME=$TIMESTAMP
        fi

        if [ $( echo "$LOAD15MIN < $MIN15MIN"|bc ) -eq 1 ]
        then
                MIN15MIN=$LOAD15MIN
                MIN15MINTIME=$TIMESTAMP
        fi

	echo ""
	echo "******* ${TIMESTAMP} (${CYCLES})*******"
	echo " 1 min: ${LOAD1MIN} / ${CPUNUM} - max: ${MAX1MIN} (${MAX1MINTIME}) min: ${MIN1MIN} (${MIN1MINTIME}) avg: ${AVG1MIN}"
	echo " 5 min: ${LOAD5MIN} / ${CPUNUM} - max: ${MAX5MIN} (${MAX5MINTIME}) min: ${MIN5MIN} (${MIN5MINTIME}) avg: ${AVG5MIN}"
	echo "15 min: ${LOAD15MIN} / ${CPUNUM} - max: ${MAX15MIN} (${MAX15MINTIME}) min: ${MIN15MIN} (${MIN15MINTIME}) avg: ${AVG15MIN}"
	sleep $SLEEPSEC
done