It may be spring outside, but HealthCare.gov seems to be ice cold.
Fewer than 70,000 people have signed up for health insurance on that federal marketplace during a tax-season grace period that began March 15 and has just 10 days left to go, officials revealed Monday.
If that paltry response doesn't improve soon, millions of people who otherwise could avoid higher Obamacare penalties will have to pay them next year.
An exact tally was not released on Monday. But the Centers for Medicare and Medicaid Services said that "as of April 13, more than 68,000 consumers have taken advantage of this opportunity." That would represent less than 2,000 people per each of the 36 HealthCare.gov states offering a grace period.
The grace period is for people who only this tax season learned they are obligated to have health insurance, learned they owe a fine for not having had coverage last year and who want to avoid an even bigger Obamacare penalty next year.
The special enrollment season was announced after open enrollment ended Feb. 15, and reflected concern by the Obama administration that many people remain unaware of both the mandate that they have health coverage and the fine for lacking it.
The fine for not having insurance in 2014 was the greater of $95 per adult or 1 percent of taxable household income. That penalty grows to the greater of $325 or 2 percent of household income this year and is due on the filing of income tax returns.
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The low tally so far for HealthCare.gov's grace period suggests that millions of people will be subject to the higher fine next year. Tax experts who spoke to CNBC recently said that not many filers were were aware of the special enrollment period.
In addition to the 36 states served by HealthCare.gov, similar grace periods are being offered in all but three states: Idaho, Massachusetts and Colorado. A national tally has not yet been released.
California's Obamacare exchange announced two weeks ago it had signed up more than 18,000 residents during the grace period there, or more than one-quarter of HealthCare.gov's current tally.
Kevin Counihan, CEO of HealthCare.gov, said in a press release Monday, "We understand the requirement to have insurance is new, which is why we're providing this last chance for those who are uninsured, are paying a fee and were not aware of or did not understand the implications of the fee with an opportunity to enroll in affordable coverage for the rest of the year."
"We hope uninsured tax filers take the next few days to learn about the options and financial assistance that is available and to enroll in a plan that meets their needs, rather than taking the risk of choosing to get by without insurance for another year."
CMS did not make Counihan available for a requested interview with CNBC.
Larry Levitt, an Obamacare expert with the Kaiser Family Foundation, said, "This special enrollment period is a safety valve for people who were confused about the individual mandate penalty and are still uninsured, but it hasn't been used a whole lot so far."
"While not very many people have taken advantage of this tax-time enrollment opportunity, it's likely had the effect of turning down the heat on the potential controversy surrounding the individual mandate," Levitt said. "There hasn't been much of a hullaballoo over the health law's requirement to have insurance this tax season, even though it's the most unpopular part of the law."
Nearly 11.7 million people had signed up for Obamacare plans nationally on HealthCare.gov and state-run insurance exchanges by the close of open enrollment.