Do you have some other measurements? slow_log, queries without indexes, low key cache usage? Load is just one metric and can be very deceiving. Do you have any backup system which hits the disks at the same time, batch jobs, or something similar? Depending on your workload, "load" can vary - it just means the writes are being queued up.

It's definitely not a good sign, but try to get more specific. I've seen servers doing heavy network I/O with "normal" load over 5 times the number of cores.

Also, unless you're doing loads of selects and very few modifications, you could gain a lot by switching to InnoDB, or XtraDB, rather than MyISAM.