The final clumps of melting snow in the backyard are no indication of snow on the slopes.

With the power of snowmaking, gone are the days when winter sports relied on Mother Nature to provide powder for skiing, snowboarding and tubing. Ski resorts in Massachusetts begin making snow as soon as temperatures drop in November and December, opening their trails long before the first snowfall.

Yet man-made snow still requires temperatures below 32 degrees Fahrenheit to keep from melting, and the temperate winter air of the last couple of months has hindered snowpack formation, even with the help of the best snow-making machines.

The culprit for these mild, snowless winter days is El Niño, a climate condition that warms water in the Pacific Ocean and disrupts normal global atmospheric pressure and wind patterns.

In the eastern United States, El Niño brings dryer, warmer winters with less snowfall throughout the winter, according to the National Oceanic and Atmospheric Administration. Instead, snow historically comes as a handful of heavy snowstorms concentrated at the end of January and early February.

Ski resorts in Massachusetts battle abnormally warm winter days and rainstorms as the companies open trails, but the weather has slowed down the process greatly; nearly a third of Berkshire East Mountain Resort, Jiminy Peak Mountain Resort and Ski Butternut’s trails and lifts remained closed last week. Yet with the onset of colder weather and snowstorms, ski resorts remain optimistic about traffic and conditions for the second half of the season.

Volatile pattern

New England’s volatile winter weather follows a freeze-thaw-freeze pattern rather than traditional powdery snow-packing over time. Berkshire East in Charlemont leans into this pattern to combat the lack of natural snow: After the rainstorm last week, Berkshire East closed on Wednesday to allow water to drain from the snow and refreeze overnight. Marketing Director Nathan Marr said the resort adds fresh snow on top of the icy base, then grooms the terrain for ideal skiing conditions.

Currently, skiers can glide down 16 of the 33 trails at Berkshire East. Marr said he would prefer the mountain to be fully open, but only natural snow can cover Berkshire East’s glades, trails weaving through trees, with ungroomed powder.

“It’s hard to say,” Marr said about when all the trails will open. “But we are optimistically looking at the forecast for next week. With the cold temperatures and significant snow in the forecast, we hope to be 100% open very soon.”

Jiminy Peak in Hancock also anticipates upcoming snowfall, but not for glade skiing.

“We love natural snow most of all, just to get snow in people’s backyard and make people want to go skiing,” said Katie Fogel, marketing director at Jiminy Peak.

Despite the wet weather, Jiminy Peak opened most of its man-made snow terrain in time for the Martin Luther King Jr. weekend. Of the 48 trails at the resort, 28 are open during the day and 24 at night. Fogel said the resort is proud of its snowmaking abilities in challenging New England weather, and the cold weather this week will only speed up the process.

“We really had to go back to terrain more frequently than in recent years,” Fogel said “It’s taking us a little longer (to open fully) as we go back and resurface those trails.”

Solid base

Despite early preparation by beginning snowmaking a week and a half from opening, Dillon Mahon, marketing director at Ski Butternut, said the Great Barrington resort was quieter during the Christmas week, a normally busy time.

“It’s difficult,” he said about making snow in warmer weather. “When it’s warm, it (snow) melts. But we have a great snow-making system so when it melts, we continue to make new snow.”

Ski Butternut copes with the temperatures by manufacturing snow as weather permits, opening up handfuls of trails in phases. So far, skiers and snowboarders can run 14 of the resort’s 22 trails, and Mahon said another trail will open for the holiday weekend.

“Right now (Jan. 8), we have a pretty solid base from like 18 to 24 inches,” Mahon said. “We’ve seen a steady increase in traffic as we have been able to open more and more trails and get more lifts online.”

In the meantime, all three resorts focus on the Martin Luther King Jr. weekend, a normally busy time for winter sports. Butternut celebrated its 60th anniversary over the weekend with food, music and fireworks. Fifteen trails opened for the celebration, each freshly groomed for a busy three days.

Jiminy Peak marches toward its goal of opening 30 trails during the day and just under those numbers for night skiing.

And Marr keeps his eyes on the weather report.

“That’s kinda what we’ve been keeping an eye on, too. This is an El Niño winter, so forecasters are predicting heavy snow in late January and February,” he said. “Last winter we had a blizzard at the end of March, and we were able to stay open later. We like natural snow, and we certainly know what to do with it!”