Where the weather numbers come from
Every figure is drawn from TTDI's measured monthly climate corpus: multi-year averages for daily highs and lows, rain days, and humidity per city, the same records our when-to-go pages and packing lists cite. Nothing here is a long-range forecast; it is climatology, which is the right tool for choosing a month.
Comparing two cities month by month answers the planning question a forecast cannot: which of two destinations is reliably drier or cooler in the window you can travel. For a trip more than two weeks out, the multi-year pattern beats any forecast you can read today.
The comparison runs in your browser from data already on the page.