Best time to visit, city by city
When to go, worked out from ten-year climate normals rather than opinion: rain days, sunshine hours, temperature and daylight, month by month. The dataset is being assembled and city pages appear here as it lands.
The climate dataset has not been fetched yet, so no city pages exist on this route. They appear automatically once the scheduled job has run. Nothing here is estimated in the meantime.
Averages beat forecasts for this question
Deciding when to take a trip is not a weather question, it is a climate question. You are not asking whether it will rain on the fourteenth, you are asking whether October is a reasonable month to be in Lisbon at all. Those need completely different data, and most sites only offer the first.
So each city page ranks the twelve months on the three things that actually decide comfort: temperature near the low twenties, how many days bring meaningful rain, and how much sun falls on an average day. Alongside them sits daylight length, which is easy to forget and changes the character of a trip more than a couple of degrees does. A dry, mild December in Reykjavik still gives you about four hours of light.
What you will not find here is a live forecast. On a statically built site it would be hours out of date before anyone read it, and the honest answer is that weather apps do that job better. We would rather answer the question they do not.
FAQ
Where do the figures come from?
Reanalysis data covering a ten-year reference period, reduced to monthly normals: days with at least a millimetre of rain, mean daily sunshine hours, and mean daily high and low. Daylight is computed separately from the sun's position, not stored.
Is this a forecast?
No, and the distinction matters. These averages describe the shape of a typical year, which is what you need when choosing between March and July. They say nothing about the week you are actually travelling.
Why not show current weather?
Because a statically built page would serve it hours stale, and a live forecast is something a thousand weather apps already do well. What almost nobody gives you is the honest month-by-month picture, so that is what we built.