The cronjob has two tasks.
[ol]
[li]Loading all external files[/li]
[li]Generating one line in the daily CSV and the SQL table[/li][/ol]
I think you are running the cron-job far to fast. Once every 5 minutes is OK.
For the external files, such as forecasts, METAR a.s.o. the cache time is (far) more than 5 minutes.
The cron-job has to check every file for its last file-modified-time and load the file when it is above 80% of the allowed age.
The graphs .csv files for today (result.csv) will accept 1 minute values, but the graphs itself has not that much room to display all those values.
And every day all those values in your sql-table are discarded also and replaced with a single line in your monthly/yearly .csv file which will be only used to display those graphs.
There is no advantage in accessing an external hosted web-server every minute 24/7 for the graphs-weather-data.
And some web-hosting companies may think that it looks like a DDOS attack and block the IP-address.
Wim
