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Thailand Weather Forecast: July 19, 2026 — Rain and Rough Seas Warning
Scattered thunderstorms are expected across Thailand for the 24-hour period from 6am July 19 to 6am July 20, 2026, driven by the southwest monsoon pushing across the Andaman Sea and Gulf of Thailand, along with a low pressure system sitting over northern Vietnam. Every region of the country will see some storm activity today, so rain gear is a good idea wherever you are. For Koh Lanta and the southern west coast, seas are mostly around 1 metre near shore but can spike above 2 metres when storms hit, and the Thai Meteorological Department (TMD) is advising mariners to navigate with caution and avoid sailing through active storm zones.
What This Means for Koh Lanta
Koh Lanta sits on the west coast south of Phuket, in the zone the TMD classifies as "South (West Coast) southern section." Today's forecast puts storm coverage at 30% for this zone, with daytime temperatures of 32-34°C, overnight lows around 24-26°C, and southwest winds at 15-30 km/h. Wave heights near shore are approximately 1 metre, rising above 2 metres in areas with active storms.
If you have boat trips, island hopping, or snorkelling planned, check sea conditions with your operator before you head out. The TMD advisory specifically warns against sailing through active storm zones, so it is worth waiting for a clear window rather than gambling on the weather.
Regional Overview
<table> <thead> <tr> <th>Region</th> <th>Storm coverage</th> <th>Night °C</th> <th>Day °C</th> <th>Wind (km/h)</th> </tr> </thead> <tbody> <tr> <td>North</td> <td>30%</td> <td>22–26</td> <td>27–36</td> <td>SW 10–20</td> </tr> <tr> <td>Northeast</td> <td>20%</td> <td>23–25</td> <td>34–37</td> <td>SW 10–20</td> </tr> <tr> <td>Central</td> <td>20%</td> <td>23–26</td> <td>35–37</td> <td>SW 10–20</td> </tr> <tr> <td>East</td> <td>30%</td> <td>23–26</td> <td>32–36</td> <td>SW 15–35</td> </tr> <tr> <td>South (East Coast)</td> <td>30%</td> <td>23–26</td> <td>34–36</td> <td>SW 15–30</td> </tr> <tr> <td>South (West Coast)</td> <td>30%</td> <td>24–26</td> <td>32–34</td> <td>SW 15–35 (north) / 15–30 (south)</td> </tr> <tr> <td>Bangkok</td> <td>20%</td> <td>25–27</td> <td>35–37</td> <td>SW 10–20</td> </tr> </tbody> </table>
Sea Conditions and Andaman Wave Heights
The upper Andaman Sea (Phang Nga northward) is seeing waves of 1-2 metres, rising above 2 metres in thundery patches, with winds 15-35 km/h. Further south toward Phuket, Krabi and Koh Lanta, waves are closer to 1 metre near shore but can exceed 2 metres when a storm passes through. The upper Gulf of Thailand has similar conditions to the upper Andaman: 1-2 metres, above 2 metres in storms.
TMD Advisories
The TMD has issued two standing advisories for today:
- Mariners: navigate with caution and avoid sailing through active storm zones
- Residents and visitors: stay alert for storm-related hazards
Practical Tips for Today
- Carry rain gear, or buy a cheap poncho from any convenience store, wherever you are in Thailand
- If you are on Koh Lanta, check with your boat operator on the morning of any trip before committing
- Storms are scattered (30% coverage locally), so breaks in the weather are likely but not guaranteed
- Stay off the water during active rain squalls, even if conditions looked fine an hour earlier
Information sourced from The Thaiger.