Forecast the blue hour

You can photograph these different weather phenomena during twilight. Our app helps you forecast the blue hour.

Blue Hour Phenomena

The blue hour is easy to predict. For this purpose, we have developed a special weather parameter for photographers in the VIEWFINDR app, with which you can forecast the blue hour.

You can observe the following weather phenomena during the blue hour:

forecast the blue hour

Forecast the blue hour with VIEWFINDR

All these phenomena are linked to the sky being free of clouds during the Blue Hour. For this purpose, VIEWFINDR has developed a special weather parameter that addresses the wishes of landscape photographers. Conventional weather apps are only capable of displaying the weather and clouds in a single location.

In order for the light to fall freely on your subject during the blue hour, the sky must be free of clouds all around. In VIEWFINDR we calculate the clouds three-dimensionally around the photo spot. This way you can predict a cloudless blue hour with VIEWFINDR. This is not available in any other app!

During the blue hour, other interesting weather phenomena can occur that are good to photograph. For all weather phenomena, the sky must be free of clouds during the Blue Hour.

blue hour prediction with our parameter


High mountain peaks, which tower above all other mountain peaks in the vicinity, can receive the orange light of the sun below the horizon during the blue hour. Either directly, or indirectly as orange scattered light in the atmosphere. It is important that this phenomenon takes place on the opposite side of the sun.

For example, if the sun is in the east at sunrise, the phenomenon of alpenglow is observed on the east side of the peaks. This means that you have to photograph towards the west, accordingly you have to find a subject in the VIEWFINDR app where you photograph in this cardinal direction.

You can display the direction of sunrise and sunset with the sun position tool. To ensure that the sky is free of clouds and that the light of the sun can fall on the mountain peaks, you must forecast the blue hour by selecting the corresponding parameter in VIEWFINDR. The higher the probability, the sooner the mountain will glow.

alpenglow in the blue hour

Twilight rays

Unfortunately, you cannot predict this phenomenon during the blue hour. However, you can be prepared for it to occur. If there is a cumulonimbus cloud or a cumulus congestus cloud at the place where the sun will rise or set, each of which can reach very high altitudes in the atmosphere, the sun can project the shadow of the cloud into the atmosphere.

Better said, the sun makes the dust in the atmosphere glow and where the light of the sun does not reach, there the dust does not glow. The sky gets interesting stripes.

To do this, the sky must be free of clouds at your photo spot, otherwise you would not be able to observe the rays in the atmosphere. In order to be able to forecast the blue hour without clouds, you use the prediction of VIEWFINDR as usual.

Twilight rays in the blue hour

Counter twilight and earth shadow arc

When the sun is just below the horizon, counter-dawn can be observed on the opposite side. The orange-red light of the sun illuminates the dust and haze of the earth’s atmosphere and makes it glow. A beautiful pink can be observed. Below this hue, a blue arc can also be seen. This is the earth’s shadow arc. The Earth’s shadow arc is actually the shadow of the Earth’s sphere in the Earth’s atmosphere.

Both shades produce magnificent colours in the sky that you can photograph during the blue hour. With our three-dimensional algorithm, we can forecast the blue hour without clouds in VIEWFINDR, so that the horizon is also free of clouds and you can photograph the colourful splendour of counter-dawn.

counter dawn in the blue hour

Noctilucent clouds

This phenomenon can only be observed between 40 and 60 degrees latitude during the summer months. Ice clouds at an altitude between 80km and 90km are illuminated by the sun during the blue hour. Bright noctilucent clouds can be predicted during the blue hour by observing the OSWIN mesospheric radar. You can find it here: LINK TO OSWIN.

If there are signals on the radar that last until sunset, it is possible to observe the noctilucent clouds in the sky to the north during the blue hour. Note: The signal on the OSWON mesospheric radar always disappears at night! Therefore you have to use webcams at night. Glowing noctilucent clouds during the blue hour are so interesting because this weather phenomenon occurs in the northern sky.

noctilucent clouds during the blue hour


Does it always have to be night for aurora? No. You can also observe the aurora during the blue hour, when the aurora is particularly bright. Again, it is crucial to be able to predict a cloudless blue hour, otherwise the clouds will block the view of the aurora.

So if you are on a photo trip in the far north, you can already wait for the aurora in the sky during the blue hour. The side of the sky opposite the sun is particularly interesting, because the sky is darkest here and the aurora borealis can be seen much faster.

Aurora during the Blue Hour