Id just try it and measure it YMMV anyway depending on the use of power saver versus someone not on power saver. None of the weather widgets I use take up much data or battery life at all. Not even enough for me to pay attention. They are way down on the list of stuff draining my battery. Hell, answering this post right now will likely take up more battery than having the widget running all day long. The checks on those are usually pretty insignificant.
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