When you first load a Clear Outside location page, you will see a table with seven rows, a weather synopsis for the upcoming week. (Clear Outside)

Clear Outside: Long-range weather forecasts

Planning a stargazing trip? Avoid cloudy nights with Clear Outside, which forecasts weather up to seven days out.

What do you do if you need to see further into the future? Will next weekend be good for astronomy? The Clear Outside website and free apps, with detailed tables, allow you analyse weather up to seven days out, helping you better plan your backyard or out-of-town astronomical adventures.

About Clear Outside

Clear Outside can be viewed through a web browser. There are also apps for Android and iOS.

Features of this program include:

  • quick red-amber-green indicator system
  • seven-day forecast
  • cloud cover
  • wind speed
  • air temperature and dew point
  • relative humidity
  • barometric pressure
  • flyovers for the International Space Station

The Clear Outside weather prediction tools show us the conditions for the next seven days and updates hourly. While it was created by the First Light Optics company in the United Kingdom, it works for locations around the world. Type in your city name and province or latitude and longitude to see predictions for your favourite observing sites.

I like the red-amber-green traffic light system used by Clear Outside. It lets me see at a glance if there’s going to be a clear patch in the next few days.

When you first load a location page (below), you will see a table with seven rows, a weather synopsis for the upcoming week. Immediately, you can tell if there will be good opportunities for visual astronomy or astrophotography if you see green blocks.

When you first load a Clear Outside location page, you will see a table with seven rows, a weather synopsis for the upcoming week. (Clear Outside)

Reading the weekly summary 

When you closely examine one row in the Clear Outside table, you will find a wealth of information.

Data about the Moon is shown in a variety of ways in Clear Outside. The phase icon immediately reveals how bright the Moon will be. | SkyNews

Data about the Moon is shown in a variety of ways (left). The phase icon immediately reveals how bright the Moon will be. You will see familiar terms such as “Waning Gibbous” and “First Quarter.” The percentage illumination is noted, too, along with rise and set times. You can hover your mouse over the Moon block for even more information, such as distance.

The right side of the table shows the red, orange, and green blocks. Green is good and highlights what we’re most interested in: clear skies. This entire table (below) can be shifted left or right according to your needs using the “Start at Current Hour” or “Center on Midnight” buttons. I like the midnight option, personally.

This entire table in Clear Outside can be shifted left or right according to your needs using the "Start at Current Hour" or "Center on Midnight" buttons. | SkyNews

Just below the coloured blocks are thin bars showing particulars about the Sun and the Moon. 

The Sun bar (below) shows yellow during daylight hours but orange at sunset or sunrise. The “blue” hour and twilight periods appear between a bright and completely darkened sky.

The Sun bar in Clear Outside shows yellow during daylight hours but orange at sunset or sunrise. The "blue" hour and twilight periods appear between a bright and completely darkened sky. | SkyNews

The Moon bar (below) alludes to the rise and set times, with grey indicating the Moon is up. Keep an eye on those circumstances to know if moonlight may impact your visual or photographic sessions.

The Moon bar in Clear Outside alludes to the rise and set times, with grey indicating the Moon is up. | SkyNews

Both of these thin bars have an orange line in the middle of the sunlit and moonlit period informing us of when the object is highest in the sky.

If you point to the Sun or Moon bars, you’ll see a pop-up with rise and set times and information about civil, nautical, and astronomical twilight times.

Examining the day report

When you click on the date block in the weekly report, the row will expand to show detailed information for the specific day (below).

When you click on the date block in Clear Outside's weekly report, the row will expand to show detailed information for the specific day. | SkyNews

Three levels of cloud are shown with values and coloured blocks. The three rows of cloud information roll up to a “Total Clouds” summary row. Dark blue blocks are good here.

Red, amber and green blocks are used for most of the other rows. Green indicates low wind, low probability of precipitation (POP), low humidity and a dew point a few degrees below the predicted air temperature. If the dew point block is orange or red, you’ll need your dew heating accessories on your telescope, eyepieces, and camera lens.

A little satellite icon indicates an opportunity to view a flyover of the International Space Station. Hover over that block for a pop-up showing the specific times and magnitude.

Happily, the Clear Outside website shows barometric pressure, an excellent indicator of future weather conditions. Watch the trend and know that rising pressure is good.

High “total” cloud values will roll up into the day summary row and trigger an amber or red indicator for the time slot.

While the website does not support stored locations, you can load pages for your favourite observing sites and then add those to your browser bookmarks or favourites.

Examining a small embedded report

Websites operated by astronomical societies or clubs may embed the “mini” or small forecast images from Clear Outside.

The miniature two-row display (below) shows the high-level summary hour-by-hour with the total cloud indicators. The combination of green and dark blue chips allude to good astronomy opportunities.

The miniature Clear Outside two-row display shows the high-level summary hour-by-hour with the total cloud indicators. | SkyNews

Using the apps

First Light Optics created a free app for iOS and Android users.

While there is a lot going on in the screen (below), the app on your mobile device shows the information from the web-site in the same way. The day summary displays red, amber or green indicators; the detailed day report shows information about clouds, the ISS, POP, temperatures and air pressure. Swipe the screen to show the other days in the week.

First Light Optics created a free Clear Outside app for iOS and Android users. | SkyNews

A nice additional feature for the Clear Outside app in your pocket: you can save locations!

It is helpful seeing weather forecasts for an entire week, but don’t forget that the further out we go, the more speculative the prediction.

All in all, Clear Outside website and apps, though built in the United Kingdom, are very useful tools for Canadian astronomers. You need them in your weather toolkit.

Blake Nancarrow is a double star aficionado, columnist for the RASC Journal, proofreader for the Observer’s Handbook and the interim chair for the RASC Observing Committee. An avid amateur astronomer, he is a member of RASC. Visit his blog at blog.lumpydarkness.com.

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