MOSCOW — Like most of those bold enough to have tried a winter assault on the Kremlin, the leaders of Russia’s budding protest movement will face a challenge at its next rally that is perhaps far greater than any government force: the weather.

Moscow has been plagued with punishing cold for weeks, and the forecast calls for temperatures to fall to as low as minus 10 on Saturday, the day of the protest. When it is that cold, it can be difficult to breathe, let alone send a Twitter message, and organizers are scrambling to come up with ideas — free tea and coffee, hundreds of Japanese space heaters — to entice people out of their homes and keep them alive long enough to make a political point.

There also have been calls for the political sermonizing to be curtailed and the rally to be kept short.

“Otherwise, many will freeze,” Grigory Chxartishvili, better known as the writer Boris Akunin, said at a meeting of the organizing committee this week. “And afterward our rally will be blamed for causing the flu and pneumonia.”