Climate and weather: what is the difference?
Weather describes the state of the atmosphere at a given place and moment, while climate describes the statistics of those states over several decades: the same physical quantities, observed at two timescales that do not obey the same rules.
The short version
Climate is what you expect; weather is what you get. The formula is worn but exact: climate tells you to pack a coat in January, weather tells you whether it will rain on Thursday.
These are not two different quantities. It is the same temperature, the same wind, the same precipitation — looked at over a day in one case, over thirty years in the other.
Why climate is more predictable than weather
This is the point that surprises people most, and it runs against intuition. Nobody knows what the weather will be on 14 August next year, yet everyone knows August will be warmer than February.
The atmosphere is a chaotic system: a minuscule error in the initial state grows exponentially, which caps deterministic forecasting at roughly two weeks. Beyond that, individual trajectories are lost.
Climate is not a trajectory forecast, it is a statistic. It is governed by energy budgets — how much the system receives from the Sun, how much it radiates back — and those budgets stay constrained even when every individual day remains unpredictable. It is the difference between predicting which card comes next and predicting the distribution after ten thousand draws.
The corollary: "we cannot forecast five days ahead, so we can say nothing about fifty years" conflates two distinct problems.
A single episode proves nothing, in either direction
A cold snap does not refute warming, and a heatwave does not on its own demonstrate it. A single event is one draw; climate is the distribution it was drawn from.
What warming changes is that distribution: it shifts the mean, which makes hot extremes far more frequent and cold extremes rarer. Heat records being broken is therefore not individually decisive — it is their rate, compared with that of cold records, that carries the information.
Both, on this site
Climate Memory serves both, in two separate trees of pages and for two separate intentions.
The climate pages give normals, records and trends over 1940 to the most recent complete year. They only move when the archive is recomputed, roughly once a year.
The weather pages give a ten-day forecast and regenerate continuously. They carry one thing other weather services do not: the departure from the day's normal — how far the coming day strays from what this place usually sees on that date. That is precisely where the two timescales meet.