For many, clothing presents the greatest challenge to packing light; it's certainly the area where the "What if ... ?" syndrome runs most rampant ("What if I'm invited to dinner with the Queen?"). This page addresses the two major issues related to this concern: choosing clothes, and keeping them clean.
To know what to leave out and what to put in; just where and just how, ah, that is to have been educated in the knowledge of simplicity. Frank Lloyd WrightChoosing Clothing.
Minimize clothing by selecting a uniform colour scheme. Keeping to no more than two (compatible) colours ensures that everything goes with everything else, thus maximizing the number of available clothing combinations.
Choose fabrics carefully: natural fabrics can sometimes be cooler, but wrinkle more easily, dry more slowly, wick more poorly, and are generally heavier than synthetics (modern synthetic yarns have come a long way from the "putrid polyesters" of yesteryear). Knitted fabrics are less prone to creasing. And small plaids/checks and other patterns, especially in darker hues, are better than solid light colours when it comes to keeping any wrinkles (and stains, and dirt) from being noticed. In all cases, the use of bundle wrapping helps considerably, by eliminating folding.
Choose clothes that will dry quickly. It's not a bad idea to test any new item you are considering by washing, towel drying, and hanging it indoors overnight. Anything not dry by morning is likely to prove annoying on a long trip (see "Doing Laundry", below).
Avoid military-styled clothing, which in some parts of the world can definitely send the wrong message. This includes anything with a camouflage pattern, or coloured green! Sounds extreme, but even green backpacks were once confiscated in Nicaragua.
Keep a watchful eye out for reversible clothing, especially tops; these effectively double your clothing choices, without noticeably increasing the amount you actually need to carry. Should you be fortunate enough to come across such an item that appeals to you, I suggest setting it aside for travel purposes only, as decent reversible clothing tends to be difficult to find! A surprisingly untapped market, in my view.
In fact, I encourage in general the notion of setting appropriate clothing aside for travel. If you travel much, you will soon come to recognize "perfect" travel wardrobe items, and it seems a shame to "waste" them on ordinary life! Reserving travel-only clothing also tends to make it less onerous to wear the same items for extended periods of time.
Pay particular attention to underwear & socks, especially on longer trips. They will have a significant effect on your comfort, and likely be much more difficult (if not impossible) to replace than your outerwear, especially in developing countries, or areas where the local people have body shapes much different than yours. It's always possible to purchase appropriate outerwear locally (it may well be more appropriate than what you brought with you, and often makes for good souvenirs); the same is not true of undergarments. Incidentally, white socks and underwear are unlikely to remain that way over time, so unless you prefer surprises, start off with a colour choice of your own!
I can't recommend the notion of disposable undergarments; it simply doesn't make a lot of sense to me. Enough such underwear & socks for a simple two-week trip would cost around $60, take up at least as much space (and weight) as what I use now, and be considerably less comfortable. Typically made of thin, cheap cotton, they provide neither the wicking function so important to socks & underwear in hot conditions, nor decent support (for men's underwear) or cushioning (for socks). And although saving me a few minutes of laundry time every 2–3 days, they would saddle me with the ecological irresponsibility of buying stuff to throw away.
A related — and frequently recommended — traveller's strategy is the packing of older clothes that you plan to discard anyway, the theory being that abandoning them along the way makes room for souvenirs. I think this is more likely to appeal to those who take too many clothes to begin with; my travel wardrobe is intentionally pretty modest in volume, so there is little space to be recovered. Further, I prefer to look (and feel) my best when out in the world, and not have my aging elastic give out in the midst of some promising adventure. If you decide to try this, however, don't just leave clothes in your hotel room, unless you'd like them returned home at your expense! Deposit them in the trash, or donate them to the service staff.
Overpacking commonly begins with too much clothing. and often this is no more than an issue of attitude. Take exercise clothing, for example. Not all that many years ago, we didn't really have anything called "exercise clothing"; people just dressed casually when exercising. It's certainly nice to have modern, specialized garments, but unless you're preparing for the Olympics, it's a luxury, not a necessity. Many of the exercise shoe companies make dual-purpose shoes that look like casual business shoes, but employ running shoe construction; they can be used effectively for both. More specialized shoes (for golf, say, or bowling) can usually be rented when required. So again, while this stuff is nice to have, one needs to decide whether or not the associated benefits are worth lugging it around wherever you go, thus foregoing the joys (and returns) of packing light. For me, there's no argument!
Deal with temperature variation by layering, not by packing heavier clothing; a set of long underwear — especially the newer technical varieties — is much more weight/bulk-efficient than a heavy coat. And because the human body loses more heat (typically 35–50%) through the head (where the skin cannot vasoconstrict) than anywhere else, wearing a hat is the most important part of keeping warm. The packing list on this site includes 5–7 layers of upper-body insulation, enough for anything short of an arctic expedition.
The other end of the scale demands that we pay closer attention. Humans are fairly tolerant of cold, and can regularly recover even from long periods of hypothermia. Raise the body temperature more than 6°F (3°C) above normal, though, and the brain malfunctions (double that figure, and all your temperature concerns will be forever eliminated).
With this in mind, have you ever noticed that the traditional garb in desert countries is not the bikini? Loose, light (in both colour and weight), long-sleeved shirts will keep you cooler than T-shirts. And, in most climatic conditions, cooler than other short- (and non-) sleeved tops as well.
The broad issue of weather, clothing, and body temperature is quite complex, and difficult to completely characterize. But the basics are straightforward ... the heat that your body is trying to get rid of arises from two sources: as a byproduct of metabolism, and heat transfer from the environment. You can reduce the former by simply slowing down; this is why the pace of life is more relaxed in regions where hot afternoons are the norm.
In very hot weather, though, most of the heat that your body is trying to eliminate has been absorbed from its surroundings. Loose-fitting, light-coloured garments that cover your skin will dramatically curtail that absorption, greatly reducing the heat that must be dissipated.
Sweating is the body's natural cooling mechanism (so remember to keep well hydrated). The efficacy of the process is related to humidity, however, which can become high enough to block evaporation entirely; when this occurs, it doesn't matter whether your sleeves are long or short: the sweat will just lie there on your skin, and provide no cooling effect. On the other hand, sun damage (which can occur very quickly in the hot sun) significantly reduces the ability of the sweat glands to function correctly, thereby reducing the body's ability to regulate itself. And long sleeves definitely defend against this.
Sure, lots of people in New Orleans wear short-sleeved shirts; people often wear what they believe will keep them cooler, rather than what actually will. But I was in New Delhi, where the temperature was 115°F (46°C) when I first wrote these paragraphs, and the great majority of local residents were wearing long-sleeved clothing.
All of this holds for the lower part of your body as well. Long pants (or skirts) will — again assuming that they are light in weight and colour — keep you cooler than shorts of any length.
And you don't need me to remind you that an appropriate hat is a useful accessory for the warm-weather traveller as well, right?
Smart travellers plan to occasionally wash clothes during the trip, one of the major secrets to living out of one small bag. This is not nearly as onerous as it might sound, if you carry the right tools. Of course, you could take your laundry to a local self-service wash ("Laundromat", "launderette"), although that:
assumes there is a local one (improbable in most locales), is likely to be expensive outside North America, and turns laundering into a major (time-consuming) event, when it can be almost as easy (and convenient) as brushing one's teeth before bedtime.
So one of your evening chores becomes doing the laundry; typically, you won't need to do so more than every other day, and if you travel with a partner, you can take turns. Wash and rinse the clothes (often only socks and undergarments) in the sink of your hotel or B&B. [Scrubbing difficult stains out of socks? Try slipping them over your hands like mittens.] Rinsing can occasionally be done more efficiently in a shower than in a sink. [Laundering silk? Try an extra/final rinse containing some hair conditioner, which (because silk — like hair — is a protein) both keeps the fabric nice and lessens wrinkles.]
Rolling wet clothes in a towel, and wringing the towel tightly (with clothes inside), is an old traveller's trick to extract water and thus considerably speed the drying process; this technique works with any towel, but using a viscose towel is particularly effective, as you can separately wring out the towel and reuse it to good effect (whereas a regular towel, once damp, will cease to be effective).
Finally, hang the garments on your travel clothesline, and go to bed. All of this takes but minutes with a bit of practice, and you will forever be amazed at how much it lightens your load.
If some item of clothing isn't quite dry when you're ready to depart in the morning, do as they do in the army: put it on anyway. Though it might feel a bit uncomfortable at first, you'll be amazed at how quickly it will dry next to a warm body. A better solution, though, is to choose travelling clothes made of quick-drying (and wrinkle-free) fabrics. A shirt made of Coolmax® (or some similar fabric) will not only dry quickly, but will keep you cooler in summer and warmer in winter than one made of cotton.
If you're travelling on business, of course, you're unlikely to want to wash your dress shirts in the sink (though it's nice to be able to). On the other hand, it's more likely that someone else is footing the bill, so letting the hotel do your laundry is a more acceptable option. Be prepared for occasional surprises if you take this route; the laundry processes in foreign hotels can be quite entertaining! Should you choose to have the proprietor of a B&B or small hotel do your laundry, make sure to negotiate the fee in advance.
When travelling for extended periods, some people like to splurge on a "real" laundry every couple of weeks or so. Drop-off laundries in some places are notorious for "losing" items; spreading out your clothing on their counter and taking a quick photo with your digital camera can help resolve any differences of opinion at pickup time.
What if I am Invited to Dinner with the Queen?
Two effective options are:
buy yourself a new outfit, and patronize a local rental service (for years, such establishments have been supplying formal wear of all types for short-term usage; you'll even find them on cruise ships).
In fact, this is the universal answer to any of the (mostly unlikely) situations presented by this kind of "What if ...? scenario. Simply ask yourself what the local populace would do should they ever need whatever item(s) you're missing!