January 23, 2017 5:21 AM EST

After five long years, it appears California’s drought is finally letting up. Thanks to a recent string of storms, more than a third of the state has now welcomed healthy precipitation, and California’s snowpack–a crucial source of water as the year progresses–has reached nearly twice its seasonal average in some parts of the Sierra Nevada. That’s a dramatic improvement over last summer, when literally every inch of the state experienced drought conditions. It’s also welcome news for Californians, who have faced a series of water restrictions since Governor Jerry Brown declared a state of emergency in early 2014. Farmers have been forced to spend heavily to maintain yields.

But the state’s water struggles are far from over. For one, nobody knows for sure how long these rains will last. Although recent precipitation has been abundant–in some places more than 80 in.–the accuracy of storm forecasting remains unreliable beyond a week. Californians know this all too well: last year, experts projected a “Godzilla” El Niño that would bring record levels of precipitation. It never materialized. “Will six weeks from now be wet?” asks Jeanine Jones, California’s interstate water-resources manager. “The skill in that kind of forecasting is just not there.”

In other words, a storm slowdown is a very real possibility–and it could leave California without enough water to make it through the dry summer. Historically, when that happens, the state has turned to groundwater stored in natural rock formations deep beneath the earth’s surface. But those reserves remain depleted after years of drought; restoring them could take years in some places, says Jones.

The quick influx of water has also created a delicate balancing act for water managers. Keeping surface reservoirs filled to the brim protects against the possibility of a sudden dry spell, but it also heightens the risk of flooding if and when future storms hit. To that end, water managers opened the Sacramento Weir floodgates earlier this month to drain reservoir water into nearby fields after projections showed local water levels would likely continue to rise. That’s a calculation that will be made across the state in the coming months.

For now, though, Jones is focused on planning and ensuring the state’s water supply come what may. “We’re halfway through our wettest season, and conditions have been encouraging,” she says. “I would say we’re cautiously optimistic.”

This appears in the January 30, 2017 issue of TIME.

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Write to Justin Worland at justin.worland@time.com.

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