After a colder and snowier-than-average winter, last week's warm weather felt like a reprieve — diners crowded restaurant patios in downtown Ann Arbor, and St. Patrick's Day revelers wandered the streets in shirtsleeves. An iced chai or coffee, advertised on sidewalk sandwich boards around town, didn't even sound like a bad idea.

For the record, Ann Arbor hit 68 degrees Thursday, 63 degrees Friday and 49 degrees on Saturday, according to the National Weather Service.

And while today marks the first official day of spring, the season's weather outlook isn't quite so rosy, forecasters say.

Beyond this week's predictions of freezing rain and snow flurries by Tuesday and into Wednesday and Thursday, spring may shape up to be cooler and wetter than usual, according to the weather service's White Lake Township office.

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St. Patrick's Day temperatures hit 68 degrees in Ann Arbor this year, and green-clad revelers gathered at Dominick's patio. Spring weather might be a little cooler than average this year, however.

Angela J. Cesere | AnnArbor.com

Blame La Nina, a natural phenomenon of cooling in the waters of the Pacific Ocean around the equator which shifts the jet stream pattern, changing the typical path of storms, explained Amos Dodson, a meteorologist with the weather service.

In Michigan, La Nina springs are traditionally cooler and wetter, which helps explain the cold, snowy winter this year. Temperatures recorded at Detroit Metro Airport were 3 degrees below average for the winter, with an average of 24.1 degrees.

At the same site, weather watchers recorded 67.5 inches of snow. The Ann Arbor area is having its fifth-snowiest winter season on record, University of Michigan weather observer Dennis Kahlbaum has previously reported.

The low temperatures may hold on through March, but a report by National Weather Service weather historian William Deedler shows an overall warming trend the last decade for the region, with five spring seasons since 2000 making the list of top 20 warmest springs since 1874.

Deedler's outlook takes into account the warming trend and calls for a spring about 1 degree warmer or cooler than comparable years, despite La Nina's effects — in other words, right about average.

For local gardeners, rainy or frosty weather will mean staying out of garden beds for the next several weeks, said AnnArbor.com gardening contributor Jim Leach.

"The soil is far too wet and any attempts to work it will only compact the soil structure," he said Sunday. "Having said that, don't stay completely out of the garden. It's the perfect time to walk the paths, look at the beds and dream."

As for weather predictions, Leach said: "Frankly, I keep an eye on the garden before I'd give an ear to the meteorologist. There are microclimates that vary even up and down a block due to buildings, trees, high places, drainage. The 'last frost date' is about as dependable as a bookie's odds on the March Madness college basketball playoffs."