If Jonna's zone is 13a and he lies between Karachi and Bombay, then the minimum temperature at sea level should not go below 18c UNLESS there is a cold wave from some snow covered mountain but the maximum temperature can easily hit 50c with 100% humidity in the rainy season. If there is a sea nearby then the year long average humidity should lie some where near 50%.
That's a pretty accurate view of my zone with the exception that it very rarely gets near 50°c and then only out in the country farther away from the Gulf. I think it is the tempering effect of the Gulf and the daily afternoon sea breeze that keeps the temps lower here. We do get to 40°+ a few degrees on occasion, mostly in the late spring right before the rains start. Humidity hovers around 50% in the dry season and around 100% in the wet season.
I don't understand your reasoning that the max temp should be 32°c on the equator though. I've been about 10°n in Panama and the temps were higher than that along the coast, in fact it seemed to be hotter than it is here. I was in Singapore once, plus I have some friends who live there, and it is hotter there than here as well. Without altitude my guess is that the avg temps would be higher closer to the equator. Day length would have something to do with it, particularly in the winter. Here we have about an hour difference in sunlight from winter to summer, an even day/night length keeps it from getting hotter in the summer but keeps it warmer in the winter.
Bottom line, the zones we are using here are designed for the USA. Melissa is extrapolating from them and creating a zone 16. I used Puerto Rico which is pretty close. I did a search in spanish for a world planting zone but didn't find one, I didn't try all combinations and may give it another go. I was thinking that there is probably a similar zone set up for Latin America but I'm not at all sure what it would be called. The Argentines have a lot of gardening information, they seem to be a nation of gardeners too. I'd be surprised if they didn't have some type of zoning since their country covers as many diverse areas as it does. Mexico really should have one too and perhaps it does and I'm not finding it. I do belong to a succulent club here at the agricultural university, I will ask about this at the next meeting.
From what I know, the ancient Maya were unaware or uninterested in any areas other than this hemisphere. They did trade up and down the coast perhaps as far as the US in the north and the South American coast to the south - mostly north/south so no date lines needed. They were incredible mathematicians and their calendar is actually more accurate than the current one, there is no need for any 'make up' days or leap years. They are enjoying the world's interest but are not concerned about the end of this Baktun or cycle. All the hotels are full though and the archeological ruins are overflowing with visitors so it's all good. The 'end of the world' special package rate hotel plus party deals are all sold out. Bars and restaurants are all having special events as well. I'm a bit underwhelmed by it all but I'm glad the current Maya are getting some recognition and some income from it.
