This is not a good time to be in a deckchair on a pavement on Fifth Avenue next to Central Park. It's hot and disgustingly muggy, and when you are not sitting in a pool of sweat you are being drenched by torrential rain accompanied by flashes of lightning.
The conditions in New York are so extreme they are almost biblical, which is appropriate because the people gathered on the pavement are here on the 21st century equivalent of a pilgrimage. Take Greg Packer, first in the queue. He has been sitting on the same spot since 5am on Monday.
By the time the moment of truth arrives he will have been waiting for 109 hours. He is paying homage to an icon, but when asked why, he can barely explain: "Because it's got everything. All you want is there."
The "it" is the iPhone, the latest offering from that sanctuary of techno-worship, Apple. Wags on the blogosphere have dubbed it the JesusPhone, and they are only half joking.
The iPhone goes on sale from today in New York and selected outlets across the US, including the Fifth Avenue Apple Store outside which Mr Packer and dozens more are camping.
So ubiquitous has Apple's marketing of the product been over the past six months, with tens of thousands of articles written and millions of internet hits, that six out of 10 Americans surveyed said they knew it was coming (compare that with the two out of 10 Americans who can locate Israel on a map).
The stakes could not be higher for Apple. The company is soaring at present, with a turnover last year of $22bn (£11bn). But to launch a gadget that costs so much more than the competition - $500 in the cheaper version, $600 at the top of the range - will be seen as a move of breathtaking genius, or arrogance, depending on its performance, on the part of its chief executive, Steve Jobs.
Steven Levy, author of the history of the iPod, The Perfect Thing, says Mr Jobs's reputation hangs on the next few months. "He is the face of the iPhone. He has been out there pushing it in a way that he has never done with any other product."
Mr Jobs called the iPhone "revolutionary" when he announced it earlier this year. Part of its potential attraction is that it pulls together functions performed by many different gadgets into one neat package. It combines the capabilities of a video-playing iPod with a high-end mobile phone that can take photos, process email like a Blackberry and surf the internet.
Early reviews from the bare handful of mortals who have been allowed to touch it have been generally good. The doyen of American technology writers, Walt Mossberg of the Wall Street Journal, concluded that "on balance [it is] a beautiful and breakthrough handheld computer".
David Pogue of the New York Times said that the web browser was a "real dazzler", adding: "Maybe all the iPhone hype isn't hype at all."
For the first time, full web pages can be displayed, and manipulated with ease on the iPhone's luxuriant glass display by scrolling with the finger. Another first is that the buttonless, keyboardless screen can pick up more than one instruction at the same time, allowing users to zoom in or out of pictures or web pages simply by stretching or closing the thumb and forefinger.
Reviewers have had gripes. They are divided by the new form of typing by touch rather than key (the Wall Street Journal loved it, the Times did not), and they are not impressed by the fact that the iPhone is not 3G, the most advanced form of communications, but depends on wireless access where available or on a very sleepy service from AT&T.
But initial reactions appear to be that the gizmo is sleek, gorgeous, and easily useable. It has found the holy grail that has until now proved to be so elusive: a mobile device that brings together all forms of digital communications - internet, email, music, videos, phone - and makes them pleasurable to experience.
"This is the next step in convergence," said Ryan Block, editor of web magazine Engadget.com. "It is taking what is already out there and making it useable for ordinary human beings."
That has always been the strength of Apple: it combines marketing brilliance with design beauty and technical functionality so seamlessly that you can hardly tell where the style ends and the substance begins. And the pilgrims love it.
Vincent Nguyen, number 11 in the Fifth Avenue queue, took the red eye flight from Arizona on Tuesday night to be here. He runs a website called myiTablet.com. "I screamed like a little girl when they announced the iPhone," he says. "I haven't slept properly ever since. I'm hoping on Saturday I'll finally find some peace."