Temperature forecast — how to read it
The temperature map shows the forecast 2-meter air temperature in °C from the DWD ICON-D2 model. It's a simple layer, but three separate VFR decisions depend on it.
How to read the color scale
Cool colors (blue / violet) are cold; warm colors (yellow / orange / red) are hot. The zero-degree contour is a visually distinct step — cross-check it if your route sits close to the freezing level.
The hover tooltip: T, Td, spread
Hover (desktop) or tap (mobile) any grid cell to reveal three numbers at once:
- T — 2 m air temperature. The one the raster is coloured by.
- Td — 2 m dewpoint. The temperature to which air would have to cool for condensation to start.
- Spread — T minus Td. A dry-air day has 15+ °C spread; a fog-imminent morning has 0–1 °C spread.
The spread is what makes this map more powerful than a plain temperature raster: it lets you spot places where the surface layer is one cold night away from fog. Anywhere on a summer evening where spread is already at 3 °C is a candidate for overnight radiation fog.
Dewpoint isolines overlay
A checkbox in the Map Controls panel toggles Dewpoint isolines on top of the temperature raster. When enabled, thin contour lines trace constant dewpoint values across the map. Three things you learn from them at a glance that the raster alone can't tell you:
- Where the humid air pools. A closed loop of high-Td isolines marks a moist tongue — often the northern side of a warm front or a valley that's held its overnight humidity.
- Where a moisture gradient sits. Isolines packed tightly together mean humidity changes fast over a small distance — the classic signature of a front. Cross-check with significant weather and precipitation.
- Where spread is thin. When a dewpoint isoline coincides with a temperature raster band at the same value, spread is zero locally — the boundary of the current fog / stratus zone.
Combined with the temperature raster, the isolines effectively give you a compact synoptic chart of the surface moisture field, time-aligned with every other map on the site.
Decision 1 — density altitude and performance
High summer temperatures at high-elevation airfields collapse piston-engine performance. A rough rule: expect a 10% loss of takeoff performance per 10 °C above ISA at your field elevation. When the map is deep orange over an Alpine strip you were planning to visit, add a performance check to your pre-flight.
Decision 2 — icing risk
A sub-zero temperature at the surface, combined with any precipitation on significant weather, means airframe icing is on the table. For structural icing you also care about the temperature column aloft, not just 2 m — for that, use a cross-section, which draws the freezing level.
Decision 3 — morning stratus burn-off
On calm autumn mornings with radiation fog, the burn-off time is driven by how fast the surface warms. Watch the temperature map's trend through the morning hours: rapid warming (5 °C in three hours) usually means the fog / stratus will lift; a stalled temperature curve says it will persist. The dewpoint isolines help here too — a persistent spread of 0 °C into mid-morning is a clear "the fog isn't going anywhere" signal.
Model caveats
2 m temperature over complex terrain has real error bars — cold-air pooling in valleys is under-resolved even at 2.1 km. Use the map for regional patterns; use the meteogram's temperature curve for a single-airfield decision.