We have a "Great Planetary Alignment" coming up, and if the weather cooperates, night sky watchers in Boston could get a glimpse of this rare sight.

You may have heard whispers about this over the last few months, but this week will be the best time to see all seven planets at one time.

Simply put, a great planetary alignment occurs when all the planets are gathered on one side of the sun.

An event like this week is fairly rare, it won't happen again this decade.

All of the planets are circling the sun on roughly the same flat, orbital plane known as the ecliptic, picture a vinyl record spinning with eight dots for planets.

So, in general, the planets will seem to be nearly aligned on an arc from our view on Earth.

How to see the planetary alignment in Boston

For our area, the best viewing of this phenomenon comes Friday and over the weekend.

What can you expect to see with and without the naked eye?

Here's the deal: Head out just after sunset on Friday evening.

You may first notice Venus, Mercury and Saturn all relatively aligned with the crescent moon in the west.

Saturn will be setting rather quickly after sunset and also very close to the setting sun, so depending on your view of the horizon, you may only catch a quick glimpse.

Mercury, Venus, Jupiter and Mars will be the easiest planets to see with the naked eye. Uranus and Neptune will require the aid of binoculars of a telescope.

Weather in Boston for planetary alignment

Perhaps the most important question of all ... will the weather cooperate?

Unfortunately, the forecast for viewing Friday night is a bit cloudy - literally.

There will be some mid and high-level clouds moving in from the west in advance of our next storm system.

So, viewing will be spotty Friday night. Some areas may be able to sneak a peek at the planets before becoming completely overcast, particularly those farthest east.

Temperatures will drop from their daytime highs in the 40s, into the upper 30s.

If you miss out Friday night, there will be more opportunities this weekend. Skies will be clearing out during the evening Saturday and Sunday will be nearly completely clear (although quite chilly).  he alignment won't be quite as perfect this weekend, but you will still be able to catch a glimpse of most of the planets.

As always, we want to see your pictures! Send them to weather@wbztv.com