Yea, that's a real challenge!
You will pass through several climate zones from blistering deserts, sticky tropics, rain and below freezing once in high Andes.

If you leave in a month ... that's perfect time of year for North America and good down to Panama. Raining season will be on the wane but you can still have PM rain.

Once in Colombia climate changes depending on altitude and proximity to coast. Once South of Santiago, Chile, things cool sharply, by late March may be too cold to ride in that far Southern section.

Best weather for Patagonia, Tierra del Fuego is October to March. (give or take) Serious Winter down there is May to September. (give or take)

Maybe spend time shopping for warmer stuff in Bogota? Most capital cities have abundance of high end fashion stores, probably good outdoor gear as well. Or go to REI store for expensive but practical fashion gear USA and Canada.

Weather should be near perfect in Sept/October until you reach USA.there Things may HEAT UP dramatically in inland areas up until late October and possibly beyond.

If you're not from this area, you may not believe just how hot it can get in September. If you stay on California coast you will have relief riding Foggy coast, while it's 105F inland. :help smilie: By late October temps usually moderate.

Will stay HOT all the way to Panama. November/December/Jan are coolest months. High humidity will begin in Southern Mexico, continue until you get over 2K meters in the Andes. Lowland Jungles will be HOT and humid until Chile and Argentina. Brazil has some tough weather too. HOT HOT HOT.

Gear I like:
X Officio underwear, Tshirts. High tech fabric, no stink, wash anywhere with very little water, dries in few hours. Light, but expensive. THE BEST I've found.

Mesh jacket and Mesh pants are nice, ideal in SUPER heat, but will freeze you when cold or even slightly cool. Conundrum. Many ride without jacket in heat (strap on to luggage). Stay covered even if just a long sleeve T-Shirt ... no matter how hot. Stay hydrated!!!!

Lightweight medium weight riding boots with Tibia protection. Gore-Tex will not help you, costs more and once wet inside, will not dry quickly. STINK.

Change socks often in wet and high humidity. In cold you can always add layers, a down vest or another Merino wool sweater.

Balaclava is good, packs to nothing, very useful in severe cold.
Always two or three pair gloves. (to replace wet ones) Try to keep water out of boots. I carry simple, cheap rain gear to wear OVER riding gear. Not 100% dry, better than nothing, can be bought and replaced nearly anywhere.

A month traveling things will begin to fall into place regards what works and what doesn't. Ditch anything not being used ... give it away! Many over pack and bring Canadian Winter riding gear into the tropics. Bad idea.

I switch between two jackets depending on conditions, length of ride.
1. Rev 'It Mesh jacket: Great in heat, not good in even slightly cool conditions,
a short ride jacket.
2. First Gear Rainier Jacket: Light fabric that flows air (not a Winter jacket), many good waterproof zippered vents (5), 5 storage pockets with two inner pockets. All waterproof zips. Good armor but I've custom fitted better foam in back and elbows areas. Very tough, wears well. Find one cheap one's used on Craig's List.