How to refresh Webhook GET?

I have a thingspeak API I made to get the temperature from a website. I have the number displayed on my Blynk app but the only time it refreshes is when I hit the actual reset button on the Arduino. How would I go about making it that the temperature updates every 30 seconds or so?

Use a timer to call the API.
Some services may limit the number of API calls that you can make over a specific time period, so check the specs of the service first.