I am trying to take updating weather data from a website that isn't mine and put a chunk of it into a generic text file every 30 minutes. The text file should not have any html tags or anything but could be delimited by commas or periods or tabs. The website generating the data puts the data in a table with no class or id. What i need is the text from one  tag and each of its individual  tags within. The  tag is on the same line number every time regardless of the updated data.
This seems a bit silly of a challenge as the method for getting the data doesn't seem ideal. I'm open to suggestions for different methods for getting an updated (hourly-twice dailyish) temperature/dewpoint/time/etc data point and for it to be put in a text file. 
With regards to automating it every 30 minutes or so, i have an automation program that can download webpages at any time interval. 
I hope i was specific enough with this rather weird(to me at least) challenge. I'm not even sure where to start. I have lots of experience with html and basic knowledge of Python, javascript, PHP, and SQL but i am open to taking code or learning syntax of other languages.
For Python

For timed tasks for N minutes create an UNIX cron job or Windows equivalent which runs your .py script regularly
Download the weather data using urllib2 module in .py script
Parse HTML using BeautifulSoup or lxml libraries
Select the relevant bits of HTML using XPath selectors or CSS selectors (lxml)
Process data and write it to a text file

The actual implementation is left as an exercise to a reader :)
Saving select updating data points from an external webpage to a text file