In your New Zealand, your rainwear is one of the most important pieces of gear you will use. It rains A LOT here, so quality rainwear will really make a difference. If you are going to spend money on anything, a good rain jacket is probably where you will get the most value for your money.
There is HUGE variety in rainwear and to go into everything now would take many more pages than you want to read. See the appendix for a glossary of terms related to rainwear.
What you need:
Breathable – the extent of this is proportionate to quality, see below for a description of what breathability means. Basically you want your jacket to be breathable while tramping, otherwise you will get all sweaty inside the jacket and end up wet anyway.
Reasonable durability, particularly on the shoulders. The reason for this is that you will be wearing a pack, which will wear on the shoulders of whatever garment you are wearing. If your rain jacket’s shoulders have a delicate fabric on them, it will ware down quickly and lose its waterproofness.
A decent hood - ideally it will be able to be cinched around your face, cinched at the back so the peak can be brought forward or back, and be helmet compatible.
Nice features to have:
Pit zips (underarm zips) – sadly lacking on many jackets, but they will improve the breathability of a jacket massively.
Small packed size
Articulated arms (an old tailors trick that means the arms of the jacket don’t ride up if you raise your arms)
Helmet Compatible Hood
Longer length – personal preference, I prefer a shorter length jacket, but the advantage of a longer length is it can cover your shorts and keep them dry, but it also adds weight.
While shopping for rainwear you will come across a dizzying array of different fabrics, all loudly touted as being superior to the competition; common ones are eVent, Gore-Tex, Pertex, NeoShell and so on. There are differences between them, but they pretty much all do the same thing. If you want to get that into the distinctions between them, have a look online.
There is a huge price range for rainwear and it generally does correspond with performance; in other words you get what you pay for (bear in mind the warnings on full retail price at the start of this guide). If you are going to spend money on anything, this is a good place to spend it, as it is the thing you can use the most outside of tramping.
As a starting point, on your first tramp, a basic school rain jacket is fine. But if you decide to get more into tramping, it is worth investing in a good quality waterproof/breathable jacket.
Over Trousers (Rainpants)
Not strictly required, on really wet or windy trips they will add to your comfort level. If the weather is good, there is really no point carrying them. In terms of buying advice, everything that is true for rain jackets is true for over trousers, although it is less worth spending money on really nice ones unless you are going to use them often. Durability is also more of an important consideration with trousers than it is with jackets.
The following is a glossary of terms associated with rainwear in an outdoor context. Rainwear is absolutely full of jargon, and it can be terribly confusing when a sales person walks up to you and says something like "this is a 3-layer eVent jacket with 30,000HH and 25000 breathability. The below glossary is your guide to what that all means. Don't feel the need to read it if you don't want to, it is purely so you can understand what the salesperson is talking about; in fact, if you can grasp all of the below, you will know more than most salespeople.
WP/BR – This stands for waterproof breathable, as in waterproof breathable fabrics. It means that the fabric is waterproof while also allowing moisture to evaporate through it, thus being breathable.
Hydrostatic Head (HH) – Hydrostatic Head is a measure of the waterproofness of a piece of material. It is usually tested by stretching a piece of material over the bottom of a clear tube, then water is slowly added to the tube until the fabric leaks. The waterproofness of the fabric is measured by how high the collumn of water gets before it leaks. The amount of water is measured in millimeters (mm). So a fabric that leaks when more than 3000mm of water is placed on top of it would be waterproof to 3000mm or HH. To be considered waterproof a fabric has to be waterproofed to a minimum of 1000mm.
Breathability – Breathability is a measure of how fast and easily sweat will evaporate from inside a piece of rainwear to the outside. So how fast your sweat will come off your body in other words. Breathability is often quoted in g/m2/24hrs; sometimes it is quoted in grams (g), but this is usually just short hand for g/m2/24hrs. Take for example Pertex Shield AP fabric, it has a breathability rating of 20,000g/m2/24hrs. What this means is that, in a 24 hour period, 20,000g of water vapour (so 20L) will pass through a square meter of the fabric. There is no universal test for breathability, different manufacturers use different test methods to arrive at the result. Even though the result is often quoted in the same unit (g/m2/24hrs), the results can vary wildly depending on the test being used. What this means in practice is that it is very hard to compare breathability across different brands. Different brands will often use the test that gives them the higher number for marketing purposes.What it is useful for is comparing different fabrics from the same brand.
DWR – Durable Water Repellent – This is the coating that is applied to the face fabric of a raincoat, also to shoes, packs and many other things. What it does is make the fabric 'water repellent' by making the indidividual fibres kind of 'spiky', so water doesn't have as much surface area to spread out. In practice this means that water beads off the fabric instead of just soaking in.. This is important because if a fabric becomes saturated with water, moisture can't evaporate from the inside of the jacket, making it less breathable. DWR coatings wear off over time, and have to be reapplied every so often. They can be revitalised by being put through the drier, or being ironed. But occasionally they have to be retreated with a product like Nikwax.
Face fabric – The layer of fabric that is on the outside of the rainwear, this is what you can see and touch. Its primary purpose is to protect the waterproof layer of a jacket, it is what gives a garment its durability. It does not give the garment its waterproofness, aside from the DWR coating.
You will often see face fabric described in terms of its denier count, or its g/m2.. Denier is a measure of the thickness of the individual fibres used in the fabric. For example, 1 denier is approximately the thickness of a single strand of silk. The higher the denier rating the more durable the fabric will be, but it will also be heavier. Rip Stop – This simply means that there are thicker fibers woven into the fabric in a cross-hatch pattern which reduces the chance of the fabric ripping, as any rip will ideally stop when it meets the thicker fiber.
Fabric Layers – When you talk about rainwear, you will often hear terms thrown around like 1 layer, 2 layer, 2.5 layer, and 3 layer construction. This refers to the number of layers of fabric in a piece of rainwear.
1 layer rainwear just uses the face fabric. These are not usually as waterproof as other constructions, as they do not incorporate a waterproof coating or membrane. They also suffer from a distinct lack of inherent breathability.
2 layer rainwear is where the waterproof coating or membrane is bonded to the face fabric, and then a separate mesh layer is sewn onto the inside of the garment to protect the waterproof membrane or coating. This type of construction is becoming increasingly uncommon, as the mesh layer adds weight and compromises breathability.
2.5 layer rainwear is similar to a 2-layer construction, except that instead of a separate mesh layer there is a very thin layer, it almost looks like a sheen, that is bonded to the waterproof layer and that protects the waterproof membrane or coating. These are very lightweight, but suffer from a lack of durability, as they wear out reasonably easily.. They are often not very breathable either, as they usually rely on a solid (as opposed to the microporous membranes used in higher end fabrics) PU coating. 3 layer rainwear is where there is the face fabric, the waterproof coating or membrane, then a another piece of fabric that is bonded to the inside of the waterproof layer. This is the most durable type of rainwear, as the inner fabric gives it a longer life span than 2.5 layer jackets. The tradeoff is that they are heavier.