Hong Kong's protestors have been using umbrellas to block tear gas, a practice that's becoming so ubiquitous that people have even started dubbed the protests the "Umbrella Revolution."

But this all started with weather — specifically, rain and sun.

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Blame it on the rain. (Aaron Tam/AFP/Getty Images)

Check out this chart of average monthly rainfall from the Hong Kong government. It rains most days in June and August, about half of the days in July, and a third in September.

hong kong rain patterns

Let the rain fall down, and cover me. (Government of Hong Kong)

So there are a lot of umbrellas floating around in late September in Hong Kong. But during the current round of protests, it happened to be unusually hot and sunny. According to the BBC, demonstrators originally brought their spare umbrellas to block out sunrays. That meant that when the police began spraying tear gas at protesters, they had a handy implement to block the toxic stuff.

The utilitarian adaptation quickly turned into an instantly recognizable symbol for the protest movement. "It's a wonderful symbol, I think, which seems to have emerged organically from [umbrellas] being used to block pepper spray and then tear gas," Jeff Wasserstrom, a UC-Irvine professor who studies protest in China, wrote via email.

Umbrellas have also become part of protest strategy. "The police have been using pepper spray quite liberally in their attempts to contain protests," Ho-Fung Hung, a sociologist of China at Johns Hopkins, told Quartz.  "The protestors are organized, they're very prepared. So you see this ocean of umbrellas on the front line."

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Rain, I don't mind / Shine, the weather's fine. (Alex Ogle/AFP/Getty Images)

The striking visual image of one man holding an umbrella amidst gas clouds is quickly becoming the iconic photograph from the Hong Kong protests. Dubbed "Umbrella Man," after the famous "Tank Man" who was photographed standing in front of Chinese army tanks during the 1989 Tiananmen protests, this unidentified protester is now a highlight of social media commentary on the protests.

Here he is, photoshopped into the original Tank Man photo:

Some protesters, according to the Washington Post's Adam Taylor, have even used umbrellas as impromptu billboards, scrawling messages on the top.

Whoever thought umbrellas could become so important?