This is an exciting world. You'll enjoy it.
Possibly you should begin here:
https://www.arduino.cc/ - walk around there a bit and see the tutorials etc on the boards and if you really want to get into it boots and all then look at one of the kits from
here or locally for you from
here and Remember - You can't beat
B4R as your IDE !!
Something to look out for:
1. Most Arduino board will accept between 5 and 12v - BUT
2. The boards put out either a 5v logic or a 3.3 volt logic - make sure they are matched
3. Serial on the boards and serial (RS232 as often referred to) are not the same thing - One runs on 5v and the other on (upto) 23v and this could have dire consequences if you connect them up directly.
Another resource for schematics, virtual breadboards (and even making PCB's afterwards) is Fritzing
here
So let's look at your project:
Firstly, you want to get a weather report and use that information to control your pool. Great idea. You could rely on an internet source or make it really interesting by getting a weather station
like this one - There are sensors included here that can check water level for you also (but now what do you when people are swimming - erratic readings - I'll leave you to figure that one out - maybe rather an ultrasonic sensor !!)
Once you have decided all this you are going to need a messaging protocol that will work faultlessly, but also let you know what is happening when you are away from home. Try MQTT, something
like this or this for
Arduino and if you want to write/keep data on the whole affair -
try this
Now you are really cooking on gas and decide you want to control your pool pump and pool lights - possibly this could be the
answer or
this (if you become lazy)
And finally, use an old tablet that is lying around as your control centre - repurpose !!
I trust that I have not confused you too much - but enjoy - this is exciting stuff !!
PS - and we have not even touched on the
pH probes,
turbidity sensors and
automatic pool valves
Enjoy !!