For planning purposes, Weatherspark is my go to website for weather at locations I may want to visit. Type in the name of a major city or airport and you get lots of data on average temperatures, probability of precip, wind, etc. Here is Witchita Kansas weather summary for spring.
https://weatherspark.com/m/145950/4/...-United-States
Note that they define a day that had precip of having at least a mm of rainfall. Thus, a day with a light mist might not be considered a day with precip. Thus, in the real world a wet day may be more common than predicted.
Assuming you will be using internet for weather forecasts, etc., you can type in a location for localized forecasts.
https://www.weather.gov/
There are other options for weather forecasts too, but I usually just use the weather service.
I believe that all of the parts of the country that you will be traveling in do not allow bicycles on interstate highways. Those highway numbers start with the letter I.
You may travel long distances without water. I usually use one liter size water bottles for touring. If you have to fill a bottle in a sink, one liter bottles do not fit under the tap, a smaller bottle may be needed to transfer water to bigger bottles. I generally start out the day with the water that I think is adequate for the whole day.
In some parts of rural western USA, you may find a shortage of restaurants too. But I will let others that have more local knowledge elaborate. Some locally owned small restaurants will not take credit cards, cash may be needed. But ATM machines are probably easy to find. That said, I would carry enough cash for several days of restaurant meals for when cash is needed.
Once you get east of Chicago, population is larger, less distance between motels and restaurants, etc.
You are smart to start planning over a year in advance.
I do not have enough travel experience in Europe to know if your European phone would have the right frequencies to work in USA or not. (I have never bought a sim card in Europe, I only used wifi with my North American phone.) Thus, I do not know if you can simply buy a local sim card here and have reliable service. That is a question for you to ask.