Sitting in his Virginia home, weather expert and US Air Force veteran David Helms has one question on his mind about far away Ukraine lately: "When does mud season stop?"

The weather there is just one more thing that troops in the trenches at the front lines have to battle. In an effort to ease the burden, retired meteorologist Helms analyzes weather that might affect the war and publishes his forecasts on social media under the hashtag "#NAFOWeather," a likely reference to the North Atlantic Fellas Organization, an online anti-Russian propaganda movement.

For the front in Ukraine, Helms has the following prediction: "The loss of moisture from the soil really picks up by May 1st and beyond," he wrote in his analysis for DW.

In southern Ukraine, the soil will be dry from around mid-April, then two weeks later in the Donetsk region, and from mid-May in the Russian-occupied Luhansk region further north, he explained.

Should the prediction turn out to be correct, it could have significant strategic meaning. While Russian tanks are still stuck in the mud in Eastern Ukraine, the Ukrainian army could begin a counteroffensive in the south toward the Russian-occupied city of Melitopol.

Helms is one of many digital volunteers worldwide who are supporting Ukraine's fight against the Russian invasion.

"To me, it's just people interested in and supporting Ukraine, trying to do whatever they can to do exactly that," he said.

He writes, for example, about when there will be "optimal optical satellite intelligence opportunities." When clear skies allow for the best photos from space, other activists then use donations to order satellite imagery from private vendors like Maxar, passing it along to Ukrainian commanders on the front lines.

Impassable terrain

This spring, forecasts from Helms have special significance: Whoever determines the regionally varying end of Ukraine's mud season gets closer to answering the much-discussed question of when the country can launch a counteroffensive to liberate land occupied by Russian forces.

Ukrainian President Volodymyr Zelenskyy has referred to the planned counteroffensive in his daily video messages. As has his defense minister, who also recently expressed his gratitude for tanks sent by the UK and Germany, in addition to German Marder infantry fighting vehicles.

In Ukraine, the mud season, known as "rasputitsa," renders fields and unpaved roads impassable for around a month in the fall and spring, due to rain and melting snow respectively. Tanks, troop carriers and artillery pieces all become mired down in the soggy earth.

"Between the amount of moisture and the volume in the top 20 centimeters of the soil, as the moisture increases, the soil strength decreases," Helms said, adding that it's a logarithmic relationship. "It changes very quickly at certain points as moisture accrues. All winter we've been accruing moisture in terms of snow and the surface of the soil has been frozen largely, although, with climate change, at times the surface layer of the soil thawed out this winter."

Flat land, black soil

The phenomenon has to do with the geography in many areas of Eastern Europe: flat land as far as the eye can see, and with a particular quality of soil. Ukraine's black earth is part of what makes the southern part of the country among the most fertile in the world.

Former military meteorologist Helms also worked for the National Oceanic and Atmospheric Administration in the US, where he studied the hydrological consequences of climate change — that is, changes in the composition of soils like what is going on just now in Ukraine.

"Mud season in the context of military vehicles depends not only on the strength of the soil, but also the kinds of vehicles that are anticipated for any offensive operation," Helms told DW. Put simply, the heft of tanks and armored personnel carriers, including how many people they carry, determines whether or not they are likely to get stuck in the Ukrainian mud.

This article was originally written in German. 

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