Cerium LT (see image) is very close to what I would call a "typical down jacket anatomy" - unlike its very thick Cerium SV and very thin Cerium SL counterparts.
Summary
CAUTION: Cerium line is designed for casual uses (very little to no output) out in mostly dry weather.
If this doesn't suit you, STOP READING HERE and visit my guide to Arc'teryx Jackets instead!
Here's the bottom line:
For winter, get the Cerium SV for freezing (down to 7 deg F (-14 deg C)) and the Cerium LT for cold (down to 28 deg F (-2 deg C)) weather. For chilly summer and spring mornings, get the Cerium SL.
Introduction
Arc'teryx's Cerium line is consists of 3 down jackets - Cerium SL, LT and SV.
They're a bit more difficult to take care of compared to synthetic jackets.
Their upsides, on the other hand, are that they're lighter, more packable and longer lasting (almost zero loss of insulation capability after many years).
You can also see the reflection of this in the chart I've put together:
Here's the list of the lowest temperatures you can wear each Arc'teryx jacket without feeling uncomfortably cold. Keep in mind that these are only approximate values assuming: Liked this table? If you did, check out this post of mine to see more Arc'teryx tables like this one, such as fill details for all down jackets. 
Name Est. Temp (F/C) Insulation Review Arc'teryx Alpha Parka (Men's - Women's) -17/-27 Down Down No M Feathered Friends Khumbu (Men's) -17/-27 Down Down No M Arc'teryx Ceres SV (Men's - Women's) -15/-26 Down Down Review Yes M Mountain Equipment K7 (Men's - Women's) -13/-25 Down Down No M Rab Positron Pro (Men's - Women's) -13/-25 Down Down No M W Patagonia Grade VII (Men's) -11/-24 Down Down No M Arc'teryx Firebee AR (Men's - Women's) -10/-23 Down Down Review Yes M W Mountain Equipment Exo (Men's) -10/-23 Down Down No M Arc'teryx Thorsen (Men's) -7/-22 Down ParkaD Review No M Patagonia Frozen Range (Men's - Women's) -6/-21 Down ParkaD Review No M W Arc'teryx Centrale (Women's) -5/-20 Down ParkaD Review No W Rab Neutrino Pro (Men's - Women's) -2/-19 Down Down No M W Arc'teryx Therme (Men's) -2/-19 Down ParkaD Review No M Arc'teryx Dually Belay (Men's) 0/-18 Synthetic Synthetic Review Yes M Arc'teryx Camosun (Men's) 0/-18 Down ParkaD Review No M Arc'teryx Piedmont (Men's) 2/-17 Down ParkaD No M Arc'teryx Fission SV (Men's - Women's) 3/-16 Synthetic Synthetic Review No M Outdoor Research Super Alpine (Men's - Women's) 3/-16 Down Down No M W Patagonia Tres 3-in-1 (Men's - Women's) 3/-16 Down ParkaD Review No M W Arc'teryx Radsten (Men's) 3/-16 Synthetic ParkaS No M Patagonia Fitz Roy (Men's - Women's) 3/-16 Down Down No M W Rab Electron Pro (Men's - Women's) 5/-15 Down Down No M W Arc'teryx Macai (Men's 5/-15 Down Down Review No M W Arc'teryx Nuclei SV Parka (Men's - Women's) 5/-15 Synthetic Synthetic No M W Patagonia DAS Parka (Men's - Women's) 5/-15 Synthetic ParkaS No M W Arc'teryx Patera (Women's) 5/-15 Down ParkaD Review No W Arc'teryx Cerium SV (Men's - Women's) 7/-14 Down Down Review Yes M W Black Diamond Access Down (Men's - Women's) 7/-14 Down Down No M W Arc'teryx Kappa (Men's - Women's) 7/-14 Synthetic Synthetic Review Yes M Arc'teryx Prema (Women's) 7/-14 Down ParkaD No W Arc'teryx Radsten Insulated Men's) 7/-14 Synthetic ParkaS No M Rab Microlight Alpine (Men's - Women's) 7/-14 Down Down No M W Patagonia Macro Puff (Men's - Women's) 8/-13 Synthetic Synthetic Review No M W Feathered Friends Eos (Men's - Women's) 8/-13 Down Down No M W Arc'teryx Macai LT (Men's) 8/-13 Down Down No M Arc'teryx Seyla (Women's) 8/-13 Down ParkaD No W Arc'teryx Koda (Men's) 8/-13 Synthetic ParkaS No M Arc'teryx Thorium AR (Men's - Women's) 8/-13 Down Down Review No M W Arc'teryx Kole (Men's - Women's) 10/-12 Down ParkaD No W Patagonia Vosque 3-in-1 (Women's) 10/-12 Synthetic ParkaS Review No W Arc'teryx Alpha IS (Men's - Women's) 12/-11 Synthetic Synthetic Yes M Patagonia Jackson Glacier (Men's - Women's) 12/-11 Down ParkaD Review No M W Arc'teryx Sensa (Women's) 14/-10 Synthetic ParkaS No W Patagonia Hi Loft Down (Men's - Women's ) 14/-10 Down Down Review No M REI Magma 850 Hoodie 2.0 (Men's - Women's) 14/-10 Down Down No M W Arc'teryx Atom AR (Men's - Women's) 18/-8 Synthetic Synthetic Review No M W Patagonia Downdrift (Men's - Women's) 18/-8 Down Down No M W Patagonia Down Sweater (Men's - Women's) 19/-7 Down Down Review No M W Arc'teryx Magnus (Men's) 19/-7 Synthetic ParkaS No M Arc'teryx Agrium (Men's - Women's) 21/-6 Down Down No M W Patagonia AlpLight Down (Men's - Women's) 21/-6 Down Down No M W Patagonia Topley (Men's) 23/-5 Down Down No M Rab Xenon 2.0 (Men's - Women's) 23/-5 Synthetic Synthetic No M W Patagonia Silent Down (Men's - Women's) 26/-3 Down Down Review No M W Mountain Hardwear Ghost Whisp/2 (Men's - Women's) 28/-2 Down Down No M W Arc'teryx Cerium LT (Men's - Women's) 28/-2 Down Down Review No M W Arc'teryx Nuclei FL (Men's - Women's) 32/0 Synthetic Synthetic Review No M W Patagonia City Storm Down (Men's) 32/0 Down ParkaD No M Arc'teryx Atom LT (Men's - Women's) 36/2 Synthetic Synthetic Review No M W Patagonia Micro Puff (Men's - Women's) 36/2 Synthetic Synthetic Review No M W Patagonia Isthmus (Men's 36/2 Synthetic ParkaS No M Arc'teryx Proton LT (Men's - Women's) 37/3 Synthetic Synthetic Review No M W Patagonia Nano Puff (Men's - Women's) 37/3 Synthetic Synthetic Review No M W Arc'teryx Norvan SL Ins. (Men's - Women's) 39/4 Synthetic Synthetic Yes M W Patagonia Nano Air (Men's - Women's) 41/5 Synthetic Synthetic Review No M W Arc'teryx Cerium SL (Men's - Women's) 43/6 Down Down Review No M W Arc'teryx Proton FL (Men's - Women's) 48/9 Synthetic Synthetic Review No M W Arc'teryx Atom SL (Men's - Women's) 52/11 Synthetic Synthetic Review Yes M W The North Face Summit Down (Men's - Women's) Testing Down Down No M W Mountain Equipment Lightline Echo (Men's) Testing Down Down No M Mountain Equipment Kryos (Men's - Women's) Testing Down Down No M W Mountain Equipment Xeros (Men's - Women's) Testing Down Down No M Arc'teryx Andra LT IS (Women's) Testing Synthetic ParkaS No W Arc'teryx Phoria IS (Women's) Testing Synthetic ParkaS No W Feathered Friends Helios (Men's) Testing Down Down No M Feathered Friends Volant (Men's) Testing Down Down No M Rab Axion Pro (Men's - Women's) Testing Down Down No M W Feathered Friends Rock & Ice (Men's) Testing Down Down No M Rab Valiance (Men's - Women's) Testing Down Down No M W Rab Expedition 8000 (Men's) Testing Down Down No M Rab Zero G (Men's) Testing Down Down No M Rab Generator Alpine (Men's) Testing Synthetic Synthetic No M UBR Regulator Parka II (Men's) Testing Synthetic ParkaS No M Helly Hansen LifaLoft (Men's - Women's) Testing Synthetic Synthetic No M Mammut Eigerjoch (Men's - Women's) Testing Synthetic Synthetic No M W Helly Hansen Lumines (Men's - Women's) Unknown Synthetic Synthetic No M Haglofs V Series Mimic (Men's - Women's) Unknown Synthetic Synthetic No M W Black Diamond First Light (Men's - Women's) Unknown Synthetic Synthetic No M W
As you see, the warmest Cerium jacket is the SV model (severe weather), while the Cerium SL (superlight) is the lightest and the Cerium LT (lightweight) is in the middle.
You can find a more detailed guide about these modifiers in Arc'teryx's Naming Scheme Page here - for all "SL", "LT" and "SV" as well as "Cerium".
Cerium SL would be perfect for chilly summer mornings before an adventure (climbing, hiking, cycling etc.).
Also...
- SV is available with the hood only (since it maximizes warmth).
- LT offers both options: With and without hoody.
- SL offers both options: With and without hoody.
Warmth Differences
Cerium jackets are insulated both with down and synthetic materials. Let's start with down insulation and see how they line up.
Down insulation
All 3 Cerium models in this post are equipped with a whooping 850 fill power European grey goose down.
If you're unaware, this value represents the amount of volume the down fully expands to at rest. The higher the FP (fill power) number, the more air will be trapped and heated inside the down, and ultimately the higher the warmth will end up being.
FP value goes up to 900 - 1000, and even the most "luxurious" parkas of Arcteryx like Thorsen, Therme, and Camosun use 750 FP down. Less than those of the Cerium's.
Cerium SL is designed to minimize the weight while naturally having to sacrifice warmth.
However, as you can guess, the amount of down is equally important. It is possible to ensure equal warmth with a lower FP down - it's just that you're going to have to use more of it and hence the jacket will be significantly heavier.
This is why the Thorsen, for example, is warmer than Cerium SV, but it's also considerably heavier (1.1 kg vs 400 g - 2.5 lbs vs 0.9 lbs).
It's the same with these jackets:
- SV: Equipped with (162 grams) 5.7 ounces of 850 FP down
- LT: Equipped with (102 grams) 3.5 ounces of 850 FP down
- SL: Equipped with (58 grams) 1.9 ounces of 850 FP down
This is why SV is the heaviest and warmest, and SL is the least warm and lightest.
Synthetic insulation
In addition to down insulation, the areas of these jackets which experience a lot of movement (such as the armpits) are also equipped with synthetic insulation (this is actually the case for all Arc'teryx down jackets):
- SV: 140 g/m² and 80 g/m² Coreloft insulation.
- LT: 100 g/m² and 80 g/m² Coreloft insulation.
- SL: 100 g/m² and 40 g/m² Coreloft insulation.
As a result, insulation loss around these areas (which typically occurs due to down migration) are minimized.
Results
Generally speaking, with only a long sleeved shirt under and without a shell on top, for an average person, during daily use (strolls, power walks, etc) and with enough wind to cause an umbrella to twist in your hand...
The approximate lowest temperatures where an average person can wear these jackets without feeling cold can be listed as:
- SV: -14 deg C (7 deg F) - ≈400 grams (≈15 oz).
- LT: -2 deg C (28 deg F) - ≈300 grams (≈11 oz).
- SL: +6 deg C (43 deg F) - ≈200 grams (≈7 oz).
If you think you run hotter or colder than the average person, mentally shift these temperatures accordingly.
Check out their current prices at the bottom of this page.
Part of the baggier cut of Cerium SV results from, again, trying to maximize the warmth.
Fit
SV is a little baggier than SL and LT.
With the baggier cut, more air trapped between your body and the jacket. As a result, more air is heated - which works as a great extra insulation. Many other insulated gear (such as sleeping bags) leverage the same principle.
There are cases where a baggier cut actually comes counter productive since it allows too much air to circulate and hence air can't get heated properly. Some even let the cold air in. But in our case it's done correctly and the baggier cut of Cerium SV perfectly adds to its warmth.
Baggier cut also lets you layer under and still stay equally comfortable when wearing the jacket - which is something to consider.
Both SL and LT come with the identical trim fit. One of their biggest pro is that they fit fantastic and provides exceptional comfort.
Face Properties
This can be another important thing to consider. Outer fabrics are quite fragile.
Waterproofing
SV and LT are DWR coated, whereas SL isn't.
DWR is a coating. It's basically sprayed on to the surface of these jackets as a finish. It stands for Durable Water Repellent - which means that water will be repelled under wet conditions instead of soaking into the fabric. DWR also decreases dry time. It's a good thing these jackets are coated in DWR, but pay attention to the fact that DWR is a coating - meaning that it will wear off over time. Which is why you might want to invest in a DWR spray such as this one for after treatment. As you see, there's a strong correlation between FP x FW and temperature ratings, but not more than, say, 80%. I explained why this happens here in this post of mine.
Still, down insulated jackets (at least say heavily down insulated jackets with little synthetic insulation besides - like Cerium) are usually more prone to losing their performances out in wet weather, compared to synthetic jackets.
This is the main downside to consider with all these jackets - even with SV.
You can say all these jackets are moisture resistant - but not water resistant.
If this is a deal-breaker for you, and hence you'd rather a truly wind & waterproof fabric instead, the reasonable substitutes for each model can be listed as follows:
- Cerium SV - Ceres SV [Read my review]
- Cerium LT - Thorium AR [Read my review]
- Cerium SL - Proton FL or Atom SL [Read my review]
Checking out this post where we listed Arcteryx's and Patagonia's top synthetic insulated jackets can be helpful as well.
Another option would be to get a hard shell on top. Cerium is a mid-layer line, after all.
Arc'teryx staff also stated the hard shell option and low water resistance performance of Cerium here:
One of the best hard shell options to wear over a Cerium is Beta AR (See Men's - See Women's). This is also stated by Arc'teryx staff as well for Cerium LT:
You can read more about Beta AR in this post of mine.
Windproofing
Mid to strong winds may (will) push through the nylon and down layers of all three Cerium models but lighter strength winds are usually blocked.
Durability
Cerium LT uses a thicker, heavier and more durable nylon both on the face fabric & lining compared to SL (Arato 10 vs Arato 7).
SV, on the other hand, is equipped with Arato 10 on the face fabric and 7 on the lining.
Still, none of these jackets are really durable as they aren't abrasion resistant. They're meant to wear under a shell in most physically active or foul weather conditions.
That does NOT mean that they can't be worn as a standalone piece, they certainly can, however, you're going to have to treat equally kind to LT, SV and SL.
They're all fragile. Most complained side of these jackets. Let's hope seeing at least a 30 or 40 fabric in future updates.
If you WILL be treating your jacket fairly kind or get a shell over it, though; you probably won't regret a fragile construction since it won't cause a negative impact.
Conclusion
If you'll be wearing your Cerium below, say, -8 deg C (17 deg F) a fair amount of days, then I'd recommend the Cerium SV.
If winters aren't really THAT cold in your town (say, above -8 deg C (17 deg F) most days), then I'd recommend Cerium LT because of its fantastic fit as well as less risk of overheating.
If you're planning to wear the jacket mainly in fall and spring (above +5 deg C (40 deg F)) during various outdoor activities such as climbing and hiking, then I'd recommend the Cerium SL.