Dry air, make water, slowly.

The Earth's atmosphere is about 20% oxygen, with only trace amounts of elemental hydrogen.  However, hydrogen is a plentiful byproduct of many terrestrial chemical reactions.  Interesting would be devising more active ways to capture hydrogen and combine it with oxygen to make water (H2O) out of thin air near points of generation before its lightness carries it into the upper atmosphere.

Green house gas methane (CH4) is a bit more abundant than hydrogen in the Earth's atmosphere.  Similar mechanisms to oxidize it near generation points would similarly allow water generation out of thin air.

Related

• treehugger/Huffington Post: Bicycle to Pull Water From the Air (added 2015-07)
• Eastern Illinois University: Origin of Earth's Atmosphere
• Answer Corporation: What percent of Earth's atmosphere is hydrogen?
• Wikipedia: Earth's Atmosphere