TPE Web provides map-based weather forecasts designed for photographers. The Weather feature brings together a curated selection of global, regional, and high-resolution weather models, with forecast layers for conditions that matter to photographers – including cloud cover, wind, fog, visibility, smoke, transparency, and seeing.
This article introduces the Weather feature, including how to select weather models, model runs, and forecast layers, and how to explore changing weather conditions over time.
Turning on Weather Forecasts
To view weather forecasts in TPE Web, select the partly cloudy Weather icon in the right-hand sidebar, then turn on the Weather switch.
Click Now to set the date and time to the present, where forecast data should be available. The selected weather forecast layer will appear on the map and, at the top of the Weather panel, you’ll see forecast conditions for the selected date and time at the primary pin location. These values are provided by Open-Meteo and may differ from the weather data shown in the selected map layer.
Weather forecasts are available for a limited number of days into the future, depending on the selected weather model and model run. The yellow line beneath the chart indicates the period covered by the selected forecast. Move the selected time to any point within this period to explore how conditions are expected to change.
- Click to open Weather panel
- Toggle on to view forecasts
- Click to go to current date and time
Forecast Layers
The Weather panel offers a variety of forecast layers showing predicted weather conditions, including cloud cover, precipitation, temperature, wind, visibility, and more.
Under Forecast Layer, select the forecast layer you want to view. The selected layer is displayed on the map, with a color-coded legend indicating the forecast values. Click the information icon next to a forecast layer to learn more about what it measures and how it may affect your photography.
NOTE: The available layers vary between models and by subscription level. Each layer is available in at least one of the supported weather models – change the model selection to see which layers are supported.
Clouds & Fog
Cloud cover is one of the most important weather conditions to consider when planning outdoor photography. Clouds can obscure the Sun, Moon, and stars, but they can also soften light, add texture to the sky, and produce beautiful colors at sunrise and sunset. The Weather panel offers forecasts for clouds at different altitudes, as well as combined cloud forecasts and specialized layers for fog and very low clouds.
High Cloud Cover
Shows the percentage of sky expected to be covered by clouds above approximately 20,000–23,000 ft (6–7 km), including cirrus, cirrostratus, and cirrocumulus. These clouds are often thin and composed of ice crystals. They can soften sunlight, produce halos around the Sun or Moon, and add color and texture to sunrise and sunset skies. Moderate high cloud cover (20–60%) can be particularly attractive for landscape photography, while even thin high clouds can reduce star contrast and detail in astrophotography.
Mid-level Cloud Cover
Shows the percentage of sky expected to be covered by clouds at approximately 6,500–23,000 ft (2–7 km), including altostratus and altocumulus. Mid-level clouds can soften sunlight, reduce contrast, or add dramatic texture to the sky. Moderate coverage (30–70%) can produce interesting conditions for landscape photography, while heavy cover may block sunlight and reduce sunrise or sunset color. For astrophotography, even partial mid-level cloud cover can interrupt long exposures.
Low Cloud Cover
Shows the percentage of sky expected to be covered by clouds from the surface to approximately 6,500 ft (2 km), including stratus, stratocumulus, and low cumulus. Low clouds can obscure mountains, skylines, or the rising and setting Sun or Moon. They can also produce soft, diffused light and atmospheric scenes. For astrophotography, even shallow low clouds can obstruct stars, the Milky Way, or auroras.
Very Low Cloud Cover
Shows the percentage of sky expected to be covered by clouds very close to the ground, typically within approximately 1,000 ft (300 m). This may include fog, mist, and low-lying stratus clouds. Very low clouds can create atmospheric conditions in forests, valleys, and mountainous areas, but may also obscure viewpoints or reduce visibility. This forecast is particularly useful when planning photographs involving low clouds or fog.
Total Cloud Cover
Shows the percentage of sky expected to be covered by clouds at any altitude. A forecast of 0% indicates clear skies, while 100% indicates overcast conditions. Total Cloud Cover provides a quick overview of expected cloudiness. Moderate coverage can create softer light and more interesting skies, while extensive cloud cover often produces flat, diffused light. For astrophotography, low total cloud cover is generally preferable, although it’s worth checking the individual cloud layers as well.
Multi-level Cloud Cover
Combines low, mid-level, and high cloud forecasts into a single color-coded map, allowing you to see where different cloud layers overlap.
Each cloud altitude is represented by a different color, and combinations of colors indicate where clouds are present at multiple altitudes. This makes it possible to distinguish, for example, an area with only high clouds from one where low clouds may obstruct the sunlight reaching them.
For sunrise and sunset photography, Multi-level Cloud Cover can help you assess where higher clouds might catch the warm light, and whether lower clouds may block the Sun near the horizon. For astrophotography, it helps identify areas with clearer skies across all three cloud levels.
Fog
Shows where fog is expected near the ground, reducing horizontal visibility. Fog consists of tiny water droplets or ice crystals suspended in the air. Fog can create atmospheric photographs in valleys, forests, along coastlines, and around lakes or cities. It often forms overnight and may be most extensive near sunrise before dissipating as temperatures rise. Fog can also obscure distant subjects, prevent clear views of the Sun or Moon, and cause condensation on photographic equipment.
Temperature & Moisture
Temperature and atmospheric moisture affect more than shooting comfort. They can influence the formation of fog, mist, frost, and condensation, as well as the performance of photographic equipment.
Air Temperature
Shows the predicted air temperature, typically measured about 2 meters (6.5 feet) above the ground. Air temperature helps photographers prepare for changing conditions, including freezing temperatures, frost, snow, and extreme heat. It can also affect battery life and equipment performance. Rapid temperature drops after sunset are particularly worth watching when planning night photography, as they can increase the risk of condensation on lenses and other equipment.
Dew Point Temperature
The dew point is the temperature at which air becomes saturated with water vapor and moisture begins to condense. It is measured in degrees Celsius or Fahrenheit, just like air temperature. When the air temperature approaches the dew point, fog, mist, or dew may develop, particularly when winds are light. This can create atmospheric conditions for landscape photography, but may also obscure distant subjects.
For astrophotography, dew point is especially important because condensation can form on lenses and telescopes when their surfaces cool to or below the dew point.
Dew Point Depression
Dew Point Depression measures the difference between the air temperature and the dew point temperature. A small difference means the air is close to saturation. For example, a dew point depression of 0–2°C (0–4°F) can indicate a greater likelihood of fog, mist, frost, or condensation.
For landscape photography, low dew point depression can help identify promising conditions for misty mornings or fog-filled valleys. For astrophotography, it can warn of an increased risk of moisture forming on lenses and other equipment, even when skies are clear. A larger dew point depression generally indicates drier air and a lower risk of condensation.
Wind
Wind conditions can affect camera stability, image sharpness, and shooting comfort. Strong winds may shake tripods, move foliage, or create rough water, while calmer conditions are often preferable for long exposures, reflections, and astrophotography.
Surface Wind Speed (10 m)
Shows the predicted average wind speed approximately 10 meters (33 feet) above the ground, a standard measurement height used in meteorology. This forecast represents sustained wind rather than short-lived gusts. Lower wind speeds are generally preferable when using tripods, long lenses, or star trackers, and when photographing reflections on calm water. Stronger winds can introduce camera shake, move foliage, and create blowing dust or spray.
Wind Gust
Shows the strongest short-lived increases in wind speed expected during a forecast period. Gusts can be considerably stronger than the average sustained wind. For photographers, sudden gusts can shake tripods, blur long exposures, and make it difficult to photograph stationary subjects sharply. They can also affect drones, light stands, and other equipment, particularly in exposed locations such as ridgelines, coastlines, and open landscapes.
Wind Gust Differential
Shows the difference between sustained wind speed and predicted wind gust speed. For example, if sustained winds are 15 mph (24 km/h) and gusts reach 30 mph (48 km/h), the gust differential is 15 mph (24 km/h). A small differential generally indicates steadier winds, while a larger differential suggests more pronounced, sudden changes in wind speed.
This forecast is particularly useful when working with tripods, long lenses, or star trackers. Even when sustained winds are manageable, strong unexpected gusts can introduce vibrations, blur photographs, or destabilize equipment.
Precipitation & Atmospheric Conditions
Rain, snow, thunderstorms, haze, and smoke can dramatically change the appearance of a scene, affecting visibility, contrast, and natural light. These forecasts can help you anticipate changing conditions, identify photographic opportunities, and prepare for potentially hazardous weather.
1-hour Precipitation Accumulation
Shows the total precipitation expected during a one-hour period, measured in millimeters or inches. This includes rain, snow, sleet, and mixed precipitation, expressed as the equivalent amount of liquid water.
Light precipitation can add atmosphere, reflections, or mist to landscape photographs, while heavier precipitation may obscure distant views and reduce contrast. This forecast is also useful for anticipating wet conditions that could affect access to a location or require additional protection for camera equipment.
Convective Available Potential Energy (CAPE)
CAPE measures the amount of energy available in the atmosphere to support rising air, which can contribute to the development of showers and thunderstorms. It is measured in joules per kilogram (J/kg). Higher CAPE values indicate greater atmospheric instability. Values above approximately 2,000 J/kg can indicate the potential for strong thunderstorms, particularly when sufficient moisture and wind shear are present. For landscape photographers, higher CAPE may signal dramatic cloud development, changing light, lightning, heavy rain, or strong winds. These conditions can offer photographic opportunities but also present significant safety risks.
Atmospheric Visibility
Shows the predicted horizontal distance you can see clearly through the atmosphere near the ground, usually measured in kilometers or miles. Visibility can be reduced by fog, mist, rain, snow, smoke, dust, or pollution. Higher visibility generally means clearer views of distant mountains, skylines, and landscapes. Lower visibility can obscure subjects but may also produce atmospheric haze, muted colors, and a greater sense of depth. For astrophotography, poor surface visibility can indicate moisture or particles in the air that may also reduce sky clarity, even when cloud cover is low.
Near-surface Smoke Concentration
Shows the predicted concentration of smoke particles close to the ground, typically measured in micrograms per cubic meter (µg/m³). Smoke near the surface can reduce visibility, soften distant landscapes, and produce hazy or unusually warm-colored light. It can also scatter moonlight and artificial light, reducing contrast in night-sky photographs. This forecast is particularly useful during wildfire season, when smoke conditions can change rapidly with shifting winds and fire activity. Check current air-quality reports when smoke is a concern.
Column-integrated Smoke
Shows the total amount of smoke particles in a vertical column of atmosphere above a location, including smoke at higher altitudes. It is commonly measured in milligrams per square meter (mg/m²). Unlike near-surface smoke, this forecast includes smoke that may be present high above the ground, even when the air near the surface appears clear. Elevated smoke can produce colorful sunrises or sunsets, but it may also reduce contrast, obscure distant views, and diminish sky clarity. For astrophotography, smoke overhead can scatter and absorb starlight, making faint stars, the Milky Way, and other celestial objects harder to photograph.
Astronomical Conditions
Clear skies aren’t the only consideration for astrophotography. Atmospheric turbulence, moisture, haze, and airborne particles can affect the sharpness and contrast of celestial objects, even when no clouds are present.
The Weather panel provides specialized forecasts for astronomical seeing and atmospheric transparency to help you assess these conditions.
Astronomical Seeing
Astronomical seeing describes how steady the atmosphere is for observing or photographing celestial objects. Turbulence in the atmosphere causes light to bend and fluctuate, making stars appear to shimmer and reducing the sharpness of astronomical images. Seeing is often measured in arcseconds, a unit of angular measurement. Lower values indicate steadier atmospheric conditions: below 1 arcsecond is considered excellent, 1–2 arcseconds is generally good, and 3–5 arcseconds or more indicates poor seeing.
Good seeing is particularly important when photographing planets, lunar details, double stars, and small deep-sky objects with long lenses or telescopes. Poor seeing can blur fine details even when the sky is otherwise clear.
Atmospheric Transparency
Atmospheric transparency describes how clearly light passes through the atmosphere without being scattered or absorbed by moisture, haze, smoke, dust, pollution, or thin clouds. High transparency means clearer skies and better contrast, making faint stars, nebulae, galaxies, and Milky Way detail easier to photograph. Poor transparency can reduce contrast and make faint objects difficult to capture, even when atmospheric seeing is good.
For landscape photography, transparency can also affect the clarity of distant mountains, skylines, and other subjects, particularly when photographing with long lenses.
For astrophotography, both seeing and transparency matter: good seeing helps preserve fine detail, while high transparency makes faint celestial objects easier to record.
Seeing + Transparency
Combines forecasts for atmospheric seeing and transparency into a single color-coded map, allowing you to assess both conditions together. Seeing describes atmospheric stability, which affects the sharpness of celestial objects. Transparency describes atmospheric clarity, which affects the visibility and contrast of stars, nebulae, galaxies, and other faint objects.
This layer is particularly useful for astrophotography, where both steady air and clear skies are important. It can help identify areas with favorable conditions for observing or photographing celestial objects.
Understanding Weather Models and Forecasts
Weather forecasts in TPE Web are generated using numerical weather prediction models produced by meteorological agencies around the world. These are computer models that use observations of current atmospheric conditions to predict how the weather will change over time.
Each weather model has its own geographic coverage, resolution, forecast duration, and available weather layers. Some cover the entire globe, while others provide more detailed forecasts for particular regions.
Weather Models
TPE Web offers a selection of global, regional, and high-resolution weather models. Higher resolution can show more local detail, but doesn’t necessarily mean that a forecast will be more accurate. It’s worth comparing models, particularly when conditions are uncertain.
- Global models (lower resolution): GFS and ECMWF
- Regional models (medium resolution): NAM (North American Mesoscale) and ARPEGE Europe (medium resolution)
- High-resolution models: such as AROME HD (France), UK Met Office, HRRR, and RAP (both North America).
NOTE: Certain weather models require a paid subscription.
Model Runs
Weather models generate new forecasts on a regular schedule – some every hour, others every 3, 6, or 12 hours. Each new set of forecasts is called a model run.
Model runs are identified by their start time in Coordinated Universal Time (UTC), also known as Zulu time, abbreviated Z. For example, 06Z means the model run started at 06:00 UTC (6:00 AM), while 18Z means it started at 18:00 UTC (6:00 PM). These are the times the model began generating its forecasts, not the times for which the weather is being predicted.
It takes time for a model to complete its calculations and for TPE Web to process the results, so the latest available run may be several hours old.
Under Model Run, select Latest to use the most recent available run, or choose an earlier run to compare predictions. Comparing runs allows you to see how a forecast is changing as new data becomes available. For example, PRO and MAX users can compare an earlier run with the latest run for the same date and time. If both predict similar conditions, that may increase your confidence in the forecast. If they differ significantly, the forecast may be less certain.
Forecast Time
The forecast time is the date and time for which the model predicts weather conditions, rather than the time the model run began.
In TPE Web, changing the selected time lets you explore how the forecast conditions are expected to change throughout the day.
Weather Display Settings
The Settings section of the Weather panel includes options to adjust how weather forecasts appear on the map:
- Desaturate map colors: Reduces the colors of the underlying map to make the weather overlay easier to distinguish.
- Forecast opacity: Choose Low, Medium, or High to control how prominently the weather layer appears over the map.
You can also use the coverage icon alongside a weather model to zoom the map to the area covered by that model’s forecasts.
