Following a very wet 2025, just 127 millimeters (mm) of rain has fallen in Tartu so far this year, marking the driest start to a hydrological year since 1961.

Last year, Estonia's second city saw rainfall totaling 712 mm.

"No two years are alike," said Ottar Tamm, assistant professor of hydroinformatics at the Estonian University of Life Sciences (EMÜ).

Hydrologists say the hydrological year, or water year, begins in November, when groundwater levels are at their lowest. Long-term data for Tartu shows median annual rainfall of about 625–650 mm.

Tamm said this year is already tracking below average, though he emphasized a summer drought isn't 100 percent guaranteed.

"I don't want to be that strict in saying we're heading for an imminent drought, since we can't predict the future," he explained. "But we can draw conclusions based on the past."

One tool used by meteorologists and scientists to compare current rainfall with long-term norms is the Standardized Precipitation Index (SPI), which looks at precipitation totals for the past three months. Values between -1 and +1 are considered normal.

"When the index moves outside that range, that's when we can say whether there's too much or too little water," Tamm said, adding that some variation in precipitation levels from year to year is entirely normal.

While Estonia has generally become wetter since the 1990s, the pattern has also gotten more extreme, with heavier but less evenly distributed rainfall.

"We see more of these spikes in recent decades," Tamm said, linking the shift toward more erratic swings to climate change.

However, that still may not help in summer, the expert warned, because heavy showers fueled by hot weather tend to run off quickly instead of soaking into dry ground.

"Most of it becomes surface runoff, flowing into rivers instead of soaking into the soil," he said.

Start conserving water now

Coastal areas and islands such as Kihnu are not currently showing signs of drought risk, but inland water levels on the mainland are expected to fall, reducing river flows and squeezing water supplies.

Tamm said urban waterways could be affected, noting that it wouldn't be a bad idea for the City of Tartu to weigh cleaning the Emajõgi riverbed this summer.

He also warned that Tallinn's water system, which depends on rivers feeding Lake Ülemiste, could come under pressure if levels drop further, and added that private wells are also at risk.

His advice? Start conserving water early.

"Those whose wells tend to run dry in summer should start thinking ahead now," Tamm said, noting that this includes making plans for backyards and gardens.

"There's no need to water green lawns," he added. "It's fine if they're a little brown."

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