What is the correct job application etiquette?

I applied to a job a few weeks ago with the final date of application on the 20th July. I still have not heard anything back however the interview date is not due until the 15th August. I would love to be able to plan my summer a little and want to contact the company so that I can find out either way but is emailing to pester about a position potentially going to go against me as being impatient or could it help, showing that I am more proactive?