"I would pay close attention to accessibility: forecasts would be in local languages..." There are many situations where somebody is interesting about the local weather but not speaking the local language. Why overwrite the users preferred language from the browser?
I suggest gatling.io as an alternative where you can record and replay browsing session while doing load testing. The tool is pretty interesting, acts as a proxy to record a browsing session and turns it into a Scala DSL code what you can modify to create close to real life scenarios.