What should Houston know about next week's freeze? Here are 5 things to keep in mind

A surge of frigid, teeth-chattering arctic air is expected to invade much of the United States early next week, plunging the nation’s temperatures, from the Rockies and the Plains to the Gulf Coast and Eastern Seaboard, into near-freezing or subfreezing levels.

How will Houston and Southeast Texas fare in this bitter blast of the polar votex? Here’s what we know:

1. A cold front arrives next week

We know a strong cold front will push into Southeast Texas on Sunday and sink temperatures to levels way below normal, which for this time of year range from as low as 43 to as high as 63. Current projections by the National Weather Service show Houston experiencing high temps in the middle to upper 40s but also lows falling below the freezing mark of 32 degrees, possibly into the mid-20s.

WEATHER EXPLAINED: What is the difference between a freeze and a frost in Southeast Texas?

What remains unknown, however, is just how low temperatures will go and where the so-called freezing line, or the boundary where freezing temperatures end, will form. In our region’s most recent freeze in mid-December, Houston temperatures stayed just above freezing, largely because of the urban heat island effect. That happens when more urbanized areas, which are made of glass, asphalt, concrete and steel, retain heat more than rural areas with more natural surroundings. This time, however, the city might succumb to the freezing temps that gripped many of Houston’s northern suburbs.

“There remains quite a bit of uncertainty on precipitation next week as it all depends on how far northward a coastal system in the western Gulf drifts,” the weather service said Thursday afternoon. “The probabilities for wintry precipitation (next) Wednesday/Thursday are low, but not zero, so be sure to stay up to the date on the latest forecasts/briefings for additional details as we get them.”

2. Expect freezing nights but thawing days

Although we don’t know the exact timing of the arrival of cold air or when it will leave Houston and Southeast Texas, we know that temperatures are expected to climb out of freezing levels during the day. The upcoming freeze could be similar to what we endured last year, during the week of the Martin Luther King Jr. Day holiday. In that 2024 freeze, Houston temperatures dropped to near or below freezing for four nights from Jan. 14-17. But daytime highs each day made it above freezing, ranging from the mid-30s to the low 50s that week.

3. This will be much worse outside of Texas

Houston actually will be on the warmest end of this cold air mass plunging into the U.S. next week, relatively speaking. The worst of the freezing blast of arctic air will be in the upper Midwest and across the eastern half of the country. The northern half of Texas also is more likely to experience 24-hour stretches of freezing temperatures.

CRAMMING FOR THE COLD?: Preparing for a freeze in Southeast Texas? Here’s a quick list of precautions to take

4. We can blame the polar vortex

The historic statewide February freeze of 2021 was the product of an outbreak of the polar vortex, which is simply an area where strong winds at high altitudes blow from west to east around the North Pole. As John Nielsen-Gammon, state climatologist and director of the Southern Climate Research Center, told the Houston Chronicle last year, the polar vortex is not the polar jet stream, per se, but it can interact with and enhance the jet stream if it moves far enough south.

Every once in a while, the polar vortex gets split into two centers of circulation, one of which can sink southward into North America. This lasts a couple of weeks before it becomes a single vortex over the Arctic again. Even if the polar vortex stays over the Great Lakes or Canada, the winds blowing from the north across Canada into the central Plains will send that cold air into Texas, Nielsen-Gammon said. This upcoming freeze also is expected to be the result of a polar vortex escaping south. 

5. You should be skeptical of social media

The weather service is warning the public to beware of “extreme scenarios on social media,” adding that “it is too soon to determine the extent of freezing temperatures and if any precipitation will occur midweek.”

Also be skeptical of long-range forecasts on weather apps on your smartphone: They often rely on a single algorithmic weather forecast model, rather than a more reliable composite of forecast models like the National Weather Service does.