In brief: A coastal low pressure system will bring (mostly) moderate rain showers into the Houston area today and tonight. Although we don’t expect any significant flooding, this will be a wet, windy, and dreary day and night. Friday is colder and windy, followed by sunnier conditions this weekend. Sunday looks rather nice with highs of about 60 degrees.
Thursday
After cold, northerly winds since Sunday evening, Houston’s pattern will now change somewhat today as winds shift to become more easterly. This is due to the presence of a coastal low pressure system that will bring increased rain chances today and tonight. Pretty much everyone will see rainfall, but how much, and when?
I think we’ll see an initial pulse of light to moderate showers this morning, with perhaps a slight reprieve during the middle of the day. The best chance of moderate or heavier showers will come later this afternoon, and especially during the evening as a slug of moisture moves up the coast from the southwest to northeast. We should then see the potential for moderate showers through the night, and possibly into the morning hours on Friday. The system should exit to the east between sunrise and noon on Friday.
Most of Houston is likely to pick up 1 to 3 inches of rainfall, and we could see some heavier bullseyes for coastal areas. I do not think these rains will cause any significant flooding issues, and therefore I am not putting a Stage 1 flood alert into place. Additionally, in the Houston metro area none of this will fall as freezing precipitation (the story could be different north of Huntsville or College Station). But do plan to take a little extra time out there because it will be fairly wet later today and tonight.

Temperatures will be in the lower 50s closer to the coast, and in the 40s further inland. The cold weather will be compounded by a strong easterly wind which may, at times, gust as high as 30 mph. So all in all, not a fun day or evening to be outside.
Friday
After the coastal low departs, we’ll see increasing northwesterly winds, and this will usher in another push of colder and drier air. So Friday will be a cold day, with highs in the lower 40s, and breezy conditions adding some wind chill on top. As skies clear out we’ll see ideal conditions for cold weather on Friday night, and much of the Houston area should see one more freeze. It will be light in Houston, but some areas in Montgomery County and to the northwest of Houston may see a hard freeze.

Saturday and Sunday
After the chilly start, the rest of the weekend looks sunny and warmer. Highs on Saturday should reach about 50 degrees, with nighttime temperatures a few degrees above freezing in the metro area. Sunday will be mostly sunny and warmer, with highs of around 60 degrees. Time to get back in the pool?
Next week
Most of next week looks to be slightly warmer, with highs in the 50s to lower 60s, and low temperatures in the vicinity of 40 degrees. This is fairly typical weather for mid-January. We’ll see a mixture of clouds and sunshine. As we head toward next weekend highs may climb toward about 70 degrees. There’s still a fair bit of uncertainty about weather for the Houston Marathon on Sunday January 19, as it looks like a front will be trying to come through next weekend. Temperatures, and any rainfall, will depend on the timing and strength of that front. Right now I’d ballpark start line temperatures at about 50 degrees, but there remains a wide variance in possibilities.