Lightweight, quick dry pants

I don't know how they are in temps above 80F but the Montane Terra Pants are the fastest drying pants I have ever used. They also have zippered thigh vents which actually aid in drying and create sort of a pumping air moving action when walking.

They are pretty durable as well.

Mike,
I will add a hearty second to Christopher's post about the Terras. I have been using them for 3 season trips for 5 years now, primarily in the Sierra, and swear by them for all the reasons he mentioned. They have functioned well for me up into the high 80's(Farenheit). We have trouble finding them these days in the US of A, but I'll bet it'll be easier for you as a member of the Commonwealth. Definitely worth checking out, IMO.

http://www.exofficio.com

Men's Amphi™ Pant (they come in zip offs too)

Try these out. They are light, dry out really fast. When I keep moving even in the worst of storms I stay really dry and rarely use rain pants until I take a rest.

I have had mine for about 5 years (my best guess). I have worn these between 1-3 days a week year around.

I don't have the weight memorized but believe them to be the same or less as the ones mentioned above. They do have a liner like a swim trunk (I have worn them for swimming and river crossings), but you can cut that out if you wish. It has one cargo pocket that has a flap and zip. The zip is great to carry some of your ten essentials.

I like Ex Officio's pants (and their Airstrip Lite shirt too) for hot weather. The REI Sahara Pants are good. Neither will hold up to bushwhacking or heavy scrub, but that is the hook with any light clothing. Running pants can be quite comfortable and available in polyester and no end of styles and colors. New Balance and Hind are quite good.

My wife wears the Exficio Amphibs and really likes them. I wear the Columbia Omni-dry and also really like them.

My size large Columbia weights 9.4 oz and
her size small Exficio weighs 8.8 oz

Both have a great feel and are very quick to dry.

I used the Marmot Drifter pants, with Cocona fabric, for five days in the Wind Rivers.
They're lightweight, 8.5oz on my pelouze scale, a high UPF rating that won't wash out, and they dry very quickly. I was primarily trail hiking, so I don't know if they can be used for bushwacking.
Overall I was pleased with the pants performance in rain and wind. They retail for $79.95, but I recently picked up a pair at REI for $34.00.
Paul