As mentioned by Stephen Ostermiller, you have several options.
1. Asking Owner
Ask the owner of the site directly. Of course, this could be a scary thought... but I think that's the best way if you are to hammer the site with so many hits in a row.
2. Check the site legal document(s)
In these documents, unfortunately, the information is most often quite general. Once in a while, though, there are useful details, especially if that document is very long... (Yeah, work.)
Since you are talking about running a script, that means you are running a robot. You need to give it a specific name that won't change and check the
robots.txt and make sure that your robot is allowed to check the site.
So if the user doesn't like it and sees your robot's name in their log, they can add a line or two to their robots.txt to block you.
4. Speed Issues
One thing that Google says about their robot (and I'm sure others do too) is that they will do the right thing to avoid flooding your website with hits that would slow down your website.
I have no idea how they have implemented that but I could imagine that they have some way to know how quickly a server answers one of their request and if further hits are answered slower, they probably slow down after that.
Because frankly, hitting a server the same URL every few seconds is probably going to be seen as an attack. When a robot, as in a spider, checks a website, at least it attempts to check all the pages of the site, not one single page.
This sounds like very old technology! A good counter is one that at least doesn't count repeat from the same IP address when hits are very close to each others (i.e. you'd save the IP for a few minutes and update the date when it needs to be deleted if the user re-access the site). That being said, you should not be too worried about one specific problem.