Before a weather model can calculate what happens next, it needs the best possible picture of the atmosphere as it is now.

As the Northern Hemisphere moves from summer into autumn, the North Atlantic atmosphere begins a seasonal reorganisation. Faster cooling at high latitudes strengthens the temperature contrast between polar and subtropical air, influencing the jet stream and creating a more favourable environment for mid-latitude weather systems.

Was last summer unusually dry? Will tomorrow’s winds be strong enough to affect outdoor work? What temperatures should a building be designed to withstand? Each question calls for weather information, but answering them requires different kinds of data.

When you open a weather app, the forecast appears simple: a temperature, a weather symbol and perhaps a probability of rain. It is easy to assume these values come directly from one weather model. In reality, model output often goes through comparison, local adjustment, observation-based updates and quality control first.

A weather forecast tells us whether tomorrow will be sunny, rainy, windy or cold. But the atmosphere contains much more than weather. Tiny particles, gases, desert dust and pollen are constantly being emitted, formed, transported and removed. Forecasting where they will be tomorrow requires meteorology and atmospheric chemistry to work together.

A 30% chance of rain sounds simple. But does it mean rain for 30% of the day, rain across 30% of the area, or that meteorologists are only 30% confident? Weather probabilities are familiar, yet they are also among the most misunderstood parts of a forecast.

A weather forecast may indicate 35°C, but that number alone rarely describes how hot the conditions will actually feel. Humidity, sunshine, wind and the surrounding environment all influence how the human body responds to heat. During a heatwave, these factors can create large differences in thermal comfort even between neighbouring locations.

Heatwaves are among Europe's most significant weather hazards, affecting millions of people as well as infrastructure, agriculture, and energy systems. But what actually causes a heatwave? Why do some persist for days or even weeks? And how do meteorologists forecast them?

Weather patterns are often connected across vast distances. A cold winter in Europe or an active Atlantic storm season can sometimes be traced back to oceanic and atmospheric anomalies occurring far beyond the region itself.

The level of detail available in weather forecasts has increased dramatically in recent years. What once focused on broad regional patterns is increasingly moving towards local, street-scale prediction. Modern forecasts can now identify which urban areas will retain heat overnight, where cold air may accumulate, or which locations face the highest risk of intense rainfall and flooding.