Mother's Day weekend is almost here and, with June just a few weeks away, most of the United States has its sights set on summer. But, in a few of the nation's nooks and crannies, winter has not yet departed. There are still pockets of cold and snow.

Among them? The peaks of the Rocky Mountains, as well as northern cities such as Marquette, Michigan, and Caribou, Maine. In some of these areas, winter began in early November and is still alive and well.

As a cold front drops out of Canada through the Rockies and the central United States this week, wintry weather will be reinforced where it lingers and will even briefly revisit some areas it had left. On Thursday, May 9, temperatures are forecast to be 15 to 20 degrees colder than normal from the Rockies to the Upper Peninsula of Michigan.

Areas where winter lingers line up well where foliage has yet to emerge on trees. In the map at the top of this report, which shows where spring has arrived through May 7, we still see voids in the Rockies, the Upper Peninsula of Michigan and northern Maine.

Let's take a tour across the country and explore in more detail where vestiges of winter remain.

1. Colorado high country

The jet stream is taking a big dip over the Central Rockies this week, inciting storminess while allowing cold, Canadian air to dive southward.

Over a foot of snow could paste some of Colorado's high elevation peaks through Thursday. Some wet snow or a rain-snow mix could even hit Denver late Wednesday night into Thursday. Just a light slushy accumulation is anticipated.

It's been a long, snowy season for the mountains of Colorado. Purgatory Ski Resort stayed open into May for the first time in its history (its final day was Sunday) and posted 362 inches of snow, third most on record.

At Rocky Mountain National Park, plow operators have yet to completely clear Trail Ridge Road, the highest paved road in the country, due to heavy snow in both March and April, according to SkyHiNews. Given the snow in the forecast this week, this effort is likely to be further delayed.

2. Arizona mountains

Some snow is even lingering in the West's southernmost state. Arizona's Snowbowl ski resort plans to remain open until May 19, the latest in its history. When it finally closes for the season, it will have been open for 160 days.

The resort has seen 332 inches of snow this season, the Arizona Daily Sun reports, the second most in the last two decades.

"Current temperatures on the mountain remain below freezing at night and in the 40s and 50s during the day," the Daily Sun notes. "According to Snowbowl, 35 ski runs are open."

3. Marquette, Michigan

On May's first day, 5.4 inches of snow blanketed Marquette, setting a record for the date. The city has received 227.1 inches of snow since last July, 10th most on record.

On April 24, Marquette finally ended a 165-day streak with at least three inches of snow on the ground.

But winter isn't finished here. The forecast for Wednesday night and Thursday this week is for cold rain, possibly mixing with snow, and a high of 37.

4. Caribou, Maine

New England's northernmost city is set to enjoy two straight days of sunny 50-degree weather but isn't yet done with cold, dismal weather.

On Friday this week, the forecast is for rain and a high of 44. That's the average high in Washington on Groundhog Day (Feb. 2). Cool, damp weather is then expected to linger in Caribou through early next week, at least.

The upcoming stretch of unsettled weather follows a decidedly bleak April.

At least a trace of precipitation fell on 20 days last month, including 11 with snow. It wasn't until April 22 that the city ended a record 163-day streak with at least an inch of snow on the ground. Caribou has received 164.7 inches of snow this year, third most on record.

This article was written by Jason Samenow, a reporter for The Washington Post.