Is the housing market grinding to a halt, or are the statistics that measure home sales still ailing from extreme weather that swept the country earlier this year? The answer to that question, expected on Tuesday, could be this week's make-it-or-break-it moment for the S&P 500 (SNPINDEX:^GSPC).

With the spring homebuying season just around the corner, the condition of the housing market has become a pivotal point of focus.

"A flurry of recent housing data suggests that the market's spring selling season is getting off to a slow start," wrote Nick Timiraos of The Wall Street Journal on Tuesday. And Robert Shiller, co-founder of the Case-Shiller Home Price Index, suggested on Friday that the market's momentum may be changing for the worse.

In short, analysts and observers are worried because of existing-home sales, which account for the lions' share of real estate activity in the United States. After climbing for nearly three straight years, the market reversed course last July. And most recently, the pace of previously owned home sales dropped by 7.1% in February compared to the same month last year.

While there are multiple explanations for the drop, one of the most frequently cited is the Arctic cold front that draped much of the country with frigid temperatures and elevated snowfall throughout the first three months of the year. "We had ongoing unusual weather disruptions across much of the country last month," said Lawrence Yun, chief economist at the National Association of Realtors.

It's for this reason that Yun believes things could soon turn around. At the end of last month, for instance, he observed that, "buyer traffic information from our monthly Realtor survey shows a modest turnaround, and some weather delayed transactions should close in the spring."

Is Yun right? Or are the issues more fundamental? That's the pivotal question analysts and investors will get an answer to on Tuesday.