For this automation we use the ESP8266-01 to drive a Relay.
It is possible make a dedicated PCB but more easy is to use a ready to use kit, we suggest this kit.
First is necessary program the right functionality (OUTPUT mode on GPIO0) in our ESP8266-01.
For the details about the program of ESP8266-01 see this guide.
Now we need to create an automation for turn ON/OFF the water valve if the weather is a partly cloudy or if is sunny.
For do this we use the Weather service.
The weather platform give us a lot of indication but we use only the partlycloudy and sunny.
First click on CONFIGURATION (1) and next on AUTOMATIONS (2), see below.
From the page that appears click on the + icon.
From the page that appears click on SKIP, see below.
From the page that appears compile the fields as shown below.
For select your trigger type, condition type, etc, press on the down arrow on its selection line.
At the end save it.
In your file AUTOMATIONS.YAML you must see something like below.