code goes here
So what happens on that line? Error in the log? What is the value of the Item? What is the type of the Item?
If you are just getting started with OH 3, I strongly recommend installing the JS Scripting add-on which will provide ECMAScript 2022 which is almost a decade more recent than Nashorn. It also has an extensive helper library that comes with it that makes interacting with OH much easier.
So my recommendation is to either:
continue to use Blockly, in OH 4 it will be converted to the newer ECMAScript for you
use Nashorn JS for this rule so you can use the code generated by Blockly to learn from
abandon using Blockly to generate examples to learn from and review the add-on docs for how to do things.
Given the docs for the newer JS, that line should be:
var valami = items.Idojarasallomas_weewxoutTemp_C.state
Note that .state returns the state of the Item as a string. If you need to do math with it use .numericState and if you need to use units use .quantityState.
Always watch openhab.log when coding. You can see them in the console. If you’ve installed openHABian Frontail is running on port 9000 which can be accessed in the browser and follows openhab.log and events.log (in MainUI it will be an option under “other uis”, the little icon in the upper right corner. But I don’t think that it can be accessed through the openHAB Cloud service, only on the LAN.