iPhone weather app - when does each "day" begin/end for high/low temperature?
If is believed thy the iPhone weather.app uses a Meteorological Day.
This is rightly sunrise to sunrise.

This is roughly sunrise to sunrise and meant to be more useful for people who are looking ahead and thinking &quot;what's the high today and the low tonight?&quot;
Check the low for the following morning (around 4 or 5am), that's probably where you'll find it.

(Source)