Seaming should proceed when ambient air temperature is between 32 -104°F (0-40° C). At temperatures below freezing, special precautions must be taken. Shielding, preheating, increasing extrudate temperature, and/or decreasing the rate of seaming may be necessary. Thawed subgrade moisture in the seam area shall not be tolerated. Frozen irregularities in the subgrade could cause problems. Temperatures outside the given range generally necessitate more frequent testing of trial welds.

High winds, or gusts of wind, always pose problems for liners. After unrolling the liner, the panels must be securely ballasted with sandbags. The seaming process, however, will necessitate the removal of some of the sandbags, which will leave any windward edge vulnerable to wind uplift. Properly orient the overlap to prevent wind uplift. Additional labor may be needed for the sole purpose of removing the sandbags immediately ahead of the seaming operation as it moves along, and immediately replacing them as the welder passes. Any dirt and moisture left behind during the movement of sandbags must be cleaned away.