The problem when caulking in colder temperatures is related to three general situations which may cause poor bonding. They are:
- The building material may be covered with a film of ice – possibly too thin to be easily visible.
- The sealant may be too cold to properly "wet down" to the applied material.
- The sealant may be too stiff to gun or tool.
Of these, only the first is a real problem. The last two are solved simply by either heating the sealant or just keeping the sealant at the suggested temperature range of 40° to 80°F prior to use such as in your vehicle. We suggest that 60° to 80°F is an ideal storage range. There are many mechanical means available for storage and maintenance of ideal temperatures. The placement of a curing type sealant at a building material temperature below 32°F is always subject to the problem described in #1 above. If the sealant is cool it may not melt the ice film. Even if it does, the pressure may be gone and the resultant water film may remain intact and act as a barrier until it freezes again. In any event the application of curing sealants to wet building materials is not recommended. Caulking can be done at low temperatures if proper care is taken to avoid the problems above. You will achieve good adhesion only if your target is clean and dry. This is easily accomplished by one of two methods:
A) Flame dry the target and apply the "warm" sealant before the surface freezes again.
B) Wipe the substrate clean of ice by using methyl ethyl ketone (MEK), which is soluble in water and may be more appropriate for winter cleaning, as it helps in removing condensation and frost. Wire brush the surface immediately before application. It should be noted that the curing time of sealants at 20°F is slowed significantly to about one-third the normal rate.
Reference: http://www.crlaurence.com/datasheets/pdfs/Sealant%20Requirement%20Estimator%20Chart%205-16-02.pdf