Field welding in winter is routine for structural fabricators working on building construction, bridge maintenance, and industrial plant expansion. AWS D1.1:2025 does not stop you from welding in cold weather, but it does impose requirements that go beyond simply matching the minimum preheat on the WPS. A CWI or QC manager who understands those requirements — and documents them in the site quality plan — prevents the three most common cold-weather welding failures: hydrogen cracking, brittle fracture from rapid cooling, and porosity from moisture contamination.
Base metal temperature: the absolute floor
The most fundamental cold-weather requirement in AWS D1.1:2025 is the minimum base metal temperature. The code prohibits welding when base metal temperature is below 0°F (-18°C). This is not a preheat threshold — it is a stop-work condition. Below 0°F, base metal toughness and ductility are reduced enough that even a well-preheated weld can encounter problems in the HAZ during cooling, and moisture in the steel lattice increases hydrogen risk dramatically.
Between 0°F and 32°F (-18°C to 0°C), welding is permitted, but the code requires that base metal within 3 inches (75 mm) of the joint be preheated to a minimum of 70°F (21°C) before the arc is struck. This 70°F minimum applies regardless of what base metal group preheat your WPS specifies. If your WPS preheat for an A572 Grade 50 joint is 50°F (10°C), but it is 25°F (-4°C) outside, you must heat to 70°F before welding — even though 50°F would otherwise be acceptable.
Measure base metal temperature with a contact thermometer (magnetic thermocouple or tempilstick). Infrared thermometers can be used, but their emissivity settings affect accuracy on mill-scale surfaces. Record the pre-heat reading in your inspection log before the root pass.
How cold affects your effective preheat
Preheat does two things: it drives out moisture and raises the base metal temperature so the weld cools slowly enough to prevent hydrogen cracking in the HAZ. In cold weather, both effects are harder to achieve and maintain.
Heat loss is faster. A joint preheated to 150°F in a 70°F shop will hold temperature for minutes before welding begins. The same joint at 20°F ambient will lose heat to the surrounding steel rapidly. On heavy section work (base metal thicker than 1 in / 25 mm), wind chills can cause the area 4-6 in from the joint to act as a heat sink, stripping temperature from the weld zone between passes.
The practical response: many QC managers and project welding engineers increase WPS minimum preheat by 50°F to 100°F on cold-weather work, and require interpass temperature verification on every pass rather than only at setup. This is not required by D1.1 but is common practice on high-restraint joints, HSLA base metals, and work where low-hydrogen crack risk is elevated.
For base metals with a carbon equivalent (CE) above 0.40 — which includes many A913, A514, A709 Gr. 70W, and similar high-strength steels — the consequence of inadequate preheat in cold weather is delayed hydrogen cracking, typically manifesting 6-72 hours after welding. Review hydrogen cracking prevention and WPS documentation for how CE values connect to minimum preheat requirements.
Wind, rain, and moisture: the site condition rules
Moisture is the other half of cold-weather welding risk. AWS D1.1:2025 requires that weld surfaces be dry — free of visible moisture from rain, snow, ice, or frost — before welding begins. Heating the base metal to the minimum preheat temperature typically accomplishes this for frost and surface ice, but driven rain and heavy snow require physical shelter.
The code does not specify a wind speed limit in numerical terms, but it requires that welding conditions allow proper shielding gas coverage and not cool the weld faster than the qualified procedure accounts for. In practice, this means:
- GMAW and FCAW-G processes are most sensitive to wind disruption of shielding gas. Most project specifications cite 5–10 mph as the practical upper limit for open-air GMAW without a wind barrier. GMAW short-circuit transfer mode is particularly vulnerable to shielding gas loss.
- SMAW and FCAW-SS (self-shielded) are much more tolerant of wind because they do not rely on an external gas column. Many infrastructure projects specify SMAW or FCAW-SS for exposed field joints for exactly this reason.
- SAW is typically not affected by wind (the flux blanket provides its own shielding) but is rarely used for cold-weather field welding.
A wind barrier can be as simple as a plywood shield clamped to the structure or a portable welding tent. The fabricator is responsible for providing and maintaining adequate shelter. The inspector is responsible for refusing to approve welds made without shelter when conditions require it.
Preheating methods and their WPS implications
AWS D1.1:2025 does not prescribe a preheating method. The three most common are:
Torch preheat (propane or oxy-fuel): Fast and portable. Risk of localized overheating and surface oxidation if the torch is held too close or too long in one spot. Move slowly, heat the full base metal mass within the 3-inch zone, and allow soak time (typically 1-2 minutes per inch of base metal thickness) before measuring temperature.
Electric resistance blanket or induction heater: Slower to set up but provides uniform heat over a large area with minimal overheating risk. Better for heavy section joints and multi-pass procedures where preheat must be maintained throughout the weld. Induction heating is increasingly common on pipeline and pressure vessel work under ASME IX, and is gaining acceptance on heavy structural members.
Propane salamander or space heater: Useful for elevating ambient temperature inside a tent or enclosure. Not sufficient by itself for direct joint preheat because it heats the air, not the steel. Combine with torch preheat for the joint zone.
The preheating method does not appear as an essential variable under Table 6.6 (D1.1:2025 essential variables for SMAW, SAW, GMAW, FCAW, GTAW), so you are not required to qualify a WPS separately for torch preheat vs. electric preheat. The WPS only specifies the minimum and maximum preheat and interpass temperatures; the site procedure or QC plan governs method.
Inspector hold points for cold weather welding
The WPS captures minimum preheat. The inspection plan must capture the procedural requirements that cold weather imposes on top of the WPS. At minimum:
- Pre-weld temperature verification hold point: Base metal temperature within 3 in of the joint, recorded by the inspector or welder, before the root pass and before each heat is re-established after a break.
- Moisture check: Visual check for frost, ice, or surface moisture before the arc is struck. Reject and re-heat if moisture is present.
- Shelter adequacy: Inspector documents that wind and precipitation conditions are controlled before approving welding to proceed.
- Interpass temperature verification: For HSLA steels or joints with high restraint, interpass temperature checks between passes documented in the weld log.
These hold points belong in the site quality plan or weld inspection data sheet, not in the WPS itself. Many shops confuse the two. The WPS is a permanent document that governs all welds made under that procedure. The site quality plan addresses the conditions of a specific project and season.
See weld inspection hold points and how CWIs should document them for how to integrate these requirements into a formal inspection record.
Documenting cold weather work in the audit packet
On public-sector projects (bridge, highway, federal buildings) and projects with owner-required audit trails, the cold-weather documentation becomes part of the construction quality record. Typical requirements:
- Daily preheat logs with time, ambient temperature, base metal temperature, welder ID, joint ID, and inspector signature
- Shelter photographs if owner requires photographic record of welding conditions
- Thermometer calibration record (contact thermometers and IR guns should be verified annually)
If your shop uses a digital WPS management system, the audit-packet export capability should allow you to attach daily field records alongside the WPS, PQR, and welder qualification records. Paper logs attached to a PDF WPS binder work, but they are harder to retrieve when an owner's representative requests records two years after the project closes.
The risk that cold weather masks
The most dangerous cold-weather welding failure is the one you do not see until it is too late. Hydrogen-assisted cold cracking (HACC) in the HAZ of an inadequately preheated joint does not necessarily show up in a same-day visual inspection. The crack forms hours to days after the weld cools, as diffusible hydrogen migrates to the crack-susceptible HAZ microstructure.
The three ingredients for HACC are: hydrogen source (moisture, low-hydrogen electrode contamination, primer decomposition), susceptible microstructure (high-CE base metal, hard HAZ from fast cooling), and tensile stress (restraint, residual stress). Cold weather amplifies all three by concentrating moisture, increasing cooling rate, and reducing base metal ductility.
Controlling preheat in cold weather is the fabricator's primary tool for breaking the HACC triangle. The WPS sets the floor; the site quality plan builds the system around it.
Rule library based on AWS D1.1:2025; verify against your governing edition.