Iowa temperatures have been warmer. Is winter behind us? These charts say not so fast

On Feb. 2, Punxsutawney Phil emerged from his burrow and saw his shadow, indicating six more weeks of winter.

On Feb. 4, two days later, the high temperature in Des Moines approached 50 degrees, and by Monday the city reached a balmy 59 degrees.

Without wanting to besmirch the reputation of the nation's foremost sciurine meteorological prognosticator — his success rate is a sterling 40%, after all — the quick turnaround in temperatures might cause some Iowans to engage in some wishful thinking: Perhaps winter has already come and gone?

The answer, unfortunately, is: Unlikely. That groundhog might be on to something after all.

The National Weather Service's Climate Prediction Center's three-month outlook for February, March and April shows equal chances of temperatures above or below normal.

In short, it's unlikely that the state will see sustained temperatures significantly warmer than usual over the next few months. That doesn't mean there won't be individual respites such as Monday, but don't count on them being a regular occurrence for a while.

Sorry, Monday's warm spell won't last

In fact, Monday's high temperature in Des Moines of 59 — not a record, but just two degrees off — was particularly rare.

Over the past 50 years, the city has reached or exceeded 59 degrees just 27 times on or before Feb. 6, including just once in the past 10.

Overall, February's gotten off to a warm start in Des Moines. Four of the six days so far have exceeded the "normal" high temperature in the city (a weather service benchmark based on the past 30 years).

Snow on the horizon

But winter is already threatening to make a return.

The National Weather Service says snow is possible as soon as Wednesday night, and while temperatures aren't expected to plummet to as cold as they were last week, some parts of the state could receive more than 2 inches of snow.

Twelve counties north of Des Moines are under a winter storm watch in advance of the expected snowfall.

When will winter leave?

So if the end of winter isn't here yet, then when?

That depends on your definition of "winter." From an astronomical standpoint, spring begins with the vernal equinox on March 20 — a date that happens to coincide with about the time Des Moines typically gets its first 70-degree day, according to the weather service.

If you think of the end of winter as the absence of cold or snow, you'll likely be waiting a little longer.

In most years, Des Moines records its first 70-degree day before it experiences its last freeze (a temperature of 28 or below). That doesn't usually happen until about April 7.

And while the normal date for the last day with at least one inch of snowfall is around March 12 in Des Moines, the last day with any snow at all is around April 4, on average.

After the first week of February, Des Moines gets a little more than a foot of snow through the rest of the winter, based on an average of all previous years on record. But that can vary wildly.

Ten years ago, Des Moines recorded more than 30 inches of snow after Feb. 7. Two years later, in 2015, the city got less than two inches after that date.

How much snow could we get?

How much will there be this year? As with temperature, the Climate Prediction Center forecasts equal chances of precipitation above or below normal over the next three months, so odds are good that there's more snowfall to come — starting with Wednesday night's forecast storm.

In other words, Phil might have been right about those six more weeks of winter, after all … if only because that's about how long winter lasts in Iowa anyway.

Tim Webber is a data visualization specialist for the Register. Reach him at twebber@registermedia.com, 515-284-8532, and on Twitter at @HelloTimWebber.

This article originally appeared on Des Moines Register: History says Iowa winter isn't over, with snow and cold still to come