textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1227 PM CST Sat Jan 17 2026

- A minor freeze is now expected across the northern ranchlands of Zapata, Jim Hogg, Brooks, and Kenedy Counties around sunrise Sunday. Tender vegetation may be damaged by the combination of low temperatures and low humidity.

- Wildfire spread danger continues at low to moderate levels this afternoon across Jim Hogg, Brooks, Kenedy, northern Starr, and northern Hidalgo County this afternoon. Very low humidity Sunday will need to be watched, though wind will be much lighter.

- Dangerous surf, gusty winds, and rough seas will continue to make boating conditions difficult through early Sunday, and life- threatening rip currents along the beach.

- Some welcome rainfall is expected mainly Wednesday and Wednesday evening favoring the coastal counties, with little to no impact on severe to extreme drought across the mid/upper Valley and Brush Country.

DISCUSSION

Issued at 1227 PM CST Sat Jan 17 2026

Rest of this afternoon through Sunday morning: Dry air has surged into the Brush Country, Rio Grande Plains, and upper RGV late this morning and north winds have increased to 15 mph with gusts over 20 mph. Skies are clearing out as well, and despite the cooler airmass, sunshine will allow temperatures to rise into the low or mid 60s in these areas. As for any rain, just enough mid/upper level moisture remains to potentially kick off a few sprinkles across the populated RGV along and just north of the Rio Grande, with no impact.

Overnight, any residual mid/high clouds clear rapidly from north to south from mid-evening to just after midnight, and low level winds back to the north-northwest at lighter speeds. Model guidance continues to vary on low temperatures, with the GFS MOS - dominated by north wind that artificially lowers temperatures too much - much colder than the other suite of deterministic models. Model blends which incorporate many model types and ensembles have nudged down a touch this morning...and are now in line with the overall sense of the weather. They now show minimum temperatures of 31/32 across the northern ranchlands. Though probabilities from the NBM (national blend) are in the 20-40% range for sub-freezing minimum temperatures, the expected combination of temperatures around freezing for 1-3 hours (6 to 8 AM) along with wet-bulb values in the upper 20s due to evaporative cooling due to low RH make the case for the freeze warning. Farther south, we still expect the coldest feels-like temperatures of the winter so far, with wind chill ranging from 30 to 35 across the populated RGV and lows between 36 and 42.

Coastal hazards of high surf and rip currents, some extreme, will prevail through daybreak. As for tidal run-up...will need to keep an eye as high tide approaches this evening as winds/seas and onshore "push" maintain. At this point, not seeing enough for water to reach the dune line, but the beach will be reduced in usable area into the overnight.

Sunday through Tuesday: A "chamber of commerce" winter day for the region, as the chilly morning quickly becomes a pleasantly cool afternoon as the Canadian-sourced surface ridge settles overhead and temperatures rebound into the low to mid 60s. The very dry airmass followed by a clear and largely calm night sets the stage for another clear and chilly start to Monday. Return flow at and just above the surface should allow low temperatures to rise about 3-5 degrees above Sunday's levels, but full radiational cooling could be enough for cold-air drainage location minor freezes to occur with perhaps some light frost north of the populated RGV. East-southeast return flow brings temperatures back to seasonable levels (low-mid 70s) Monday afternoon under some increase in mid-high clouds. By Monday night and Tuesday, mid/high clouds increase more robustly ahead of a developing diffluent area aloft moving toward northern Mexico and the Big Bend. This will keep lows noticeably milder overnight...though only a few degrees above seasonal averages (seasonal averages are between 48 and 53). Skies should be overcast Tuesday with an increasing potential for light showers/rain as the day wears on and the aforementioned diffluent zone/weak impulse approaches. Temperatures under the clouds will dip a bit to slightly below average.

Dangerous surf and rip currents will continue through the morning, with steady improvement thereafter through rips will continue until sunset. With surf temperature falling close to 60, few will be out - but for those in wetsuits caution needs to be taken.

Tuesday Night through Thursday: Scattered to potentially numerous showers remains in the forecast as a weak but notable upper level trough slides through northern Mexico and into northeast Mexico, with clouds lowering further and sufficient lift is present for precipitation. Model blends and trends continue to favor locations that need rain least...mainly the coastal counties which are largely in dryness/moderate drought (vs. severe to extreme drought)...though Kenedy County is drier than the lower RGV and has the potential to see 0.5 to 1" of rain during this event. Weak return flow will nudge temperatures up, especially overnight through early Thursday, and daytime temperatures will slide upward as well. The wave should move east and northeast by early Thursday, ending the rain though pesky clouds may remain through midday especially across the lower/mid RGV. Light to moderate north/northeast flow behind the wave, and temperatures currently forecast to be well into the 70s may end up several degrees lower - but still plenty comfortable for January.

Thursday night through Saturday: Global models have some not- surprising differences as we get into the start of next weekend, but the main storyline to close out the work week and enter next weekend is a notable warm-up, especially by Saturday, as subtropical ridge aloft builds back into the RGV/Deep South Texas. Return southerly flow brings daytime temperatures back into the 80s and morning lows in the 60s (upper 50s ranchlands), 5 to 10 degrees above average.

AVIATION

(18Z TAFS) Issued at 1227 PM CST Sat Jan 17 2026

Gusty north winds and mid-range VFR ceilings will be the rule this afternoon and early evening across Valley terminals, with skies clearing fairly rapidly from northwest to southeast by mid evening (McAllen) to around midnight (Brownsville). Winds will diminish as well, though Brownsville and Harlingen may still see 10-13 knots until just before daybreak Sunday. Light north winds and clear skies follow through noon Sunday.

MARINE

Issued at 1227 PM CST Sat Jan 17 2026

Now through Sunday: Small Craft Advisory conditions for wind and seas are well in hand, and with gradient tightening a bit further this afternoon/evening and cold advection over the water peaking, expect sustained north winds to do the same this evening into the post-midnight hours at 25 knots with gusts to 30 knots, and seas building up to 10 feet. Conditions will begin to improve slowly toward daybreak Sunday, and more rapidly by mid morning and beyond as winds rapidly decrease and seas/waves follow a bit thereafter. Small Craft Advisory for seas will likely need to be extended a bit in the Gulf to account.

Sunday night through Tuesday: Light veering winds to the east, with some increase by Tuesday, as surface high pressure ridge recedes to the north/northeast of the waters. Seas will settle into moderate ranges (3-5 feet) for the period with fair weather, though isolated showers may develop later on Tuesday.

Tuesday night through early Thursday: Southeast flow develops as the upper level disturbance moves into the region, with scattered to numerous showers becoming the rule especially Wednesday and Wednesday night - some which may reduce visibility to or below 1 nm. Not expecting thunder at this point but will need to watch, especially over the outer legs. Seas rise a touch but should hold below advisory levels.

Late Thursday through Thursday night: Conditions will be determined by the strength of the gradient behind the aforementioned wave. A reasonable worst-case would be the development of north/northeast flow up to 20 knots with higher gusts, and seas back up to 7 feet. Current forecast splits difference among models with winds closer to 15 knots and seas 4-5 feet. Though skies clear, boating conditions may worsen...so mariners should keep tabs for updates.

FIRE WEATHER

Issued at 1227 PM CST Sat Jan 17 2026

Elected to hoist a short-fused Red Flag Warning for the northern ranchlands (Inland Kenedy to Zapata) based on gusty north winds combined with RH falling to 8 to 12 percent for the next few hours (closer to 15 percent in Kenedy), overtop dry fuels and in the current severe to extreme drought area. North winds have generally been 15-19 mph with gusts to 20-29 mph and expect these conditions to continue through 4 PM, before winds diminish. Buffered the warning until 5 PM. RH may continue to flirt with 15-20 percent thereafter, but with lighter winds will not meet the "15 (mph) 15 (percent RH) rule.

As for Sunday...very low RH is expected once again, following an overnight with minimal RH recovery (40s percent) and an edge-of- curing situation. Fortunately, winds will be light - but still a modest concern based on fuel condition.

CLIMATE

Issued at 1227 PM CST Sat Jan 17 2026

Winter 2025/2026 has been relatively non-descript thus far when it comes to cold temperatures. There have been a number of days when minimum temperatures fell 5 to 10 degrees below average, but for the most part that has meant upper 30s to lower 40s in the ranchlands and in the 40s across the lower/mid Valley. Sunday morning will bring the temperatures to or below the coldest of the season, so far for many in the region.Below is the forecast low temperature, and the coldest low temperature so far to date since December 1.

Location Jan. 18 Forecast Coldest So Far (Date)

Brownsville 45 46 (Dec. 31) Harlingen/Valley 38 40 (Jan. 15) McAllen/Miller 40 46 (Dec. 7 and Jan. 15) Edinburg (City) 39 45 (Jan. 15 latest) Weslaco 39 44 (Dec. 9) Raymondville 38 40 (Dec. 31 Rio Grande City 36 37 (Jan. 15) McCook 36 42 (Dec. 31)

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 45 65 46 72 / 10 0 0 0 HARLINGEN 38 64 39 73 / 10 0 0 0 MCALLEN 40 65 43 75 / 10 0 0 0 RIO GRANDE CITY 35 65 38 75 / 0 0 0 0 SOUTH PADRE ISLAND 54 60 53 68 / 10 0 0 0 BAYVIEW/PORT ISABEL 46 63 46 71 / 10 0 0 0

BRO WATCHES/WARNINGS/ADVISORIES

TX...Red Flag Warning until 5 PM CST this afternoon for TXZ248>251.

Freeze Warning from 4 AM to 9 AM CST Sunday for TXZ248>251.

High Rip Current Risk through Sunday afternoon for TXZ451-454- 455.

High Surf Advisory until 9 AM CST Sunday for TXZ451-454-455.

GM...Small Craft Advisory until 9 AM CST Sunday for GMZ130-132-135- 150-155-170-175.