CPU utilization spike every night

cron.daily is configured by /etc/anacrontab:

[root@f5-1:Active:In Sync] config  cat /etc/anacrontab
 /etc/anacrontab: configuration file for anacron

 See anacron(8) and anacrontab(5) for details.

SHELL=/bin/sh
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
 the maximal random delay added to the base delay of the jobs
RANDOM_DELAY=45
 the jobs will be started during the following hours only
START_HOURS_RANGE=3-22

period in days   delay in minutes   job-identifier   command
1       5       cron.daily              nice run-parts /etc/cron.daily
7       25      cron.weekly             nice run-parts /etc/cron.weekly
@monthly 45     cron.monthly            nice run-parts /etc/cron.monthly

There are interesting options like "START_HOURS_RANGE" or "RANDOM_DELAY". But my cron is not customized, so I suppose, that this is general behavior. Maybe someone else have noticed same behavior.