I would read the can of deck sealant and pay attention to the dry time and lowest temperature at which it can be applied.

Adding to what Graywings said, look at the specifications for several different stain and sealant products because they may prescribe different application temperatures. I know this is true for house paints. Generally, the wood should be dry, and the temperature should be 50 degrees F for at least 48 hours after applying. If you've already had a frost warning in your area, your nighttime temperatures are probably below 50 degrees.

I would also be concerned about the amount of moisture in the wood. You won't get good results if the moisture content in the wood is too high. The moisture content would probably be too high at this time of year.

At this point, I'd wait until late spring/early summer to tackle these projects. Make sure the wood is thoroughly dry and the pollen level is low. If you wait until summer, the pollen content would be lower, but you'd have to avoid times where the humidity is high and/or temperatures are over 90 degrees.

In sum, there really ISN'T a perfect time to take this on, so your procrastination is entirely justifiable.

Why not plant some bulbs? There's still time for that.

Just what the procrastinator wanted to hear -- Thanks, graywings and dilettante! I did at least get a quote, so I can ask them if they'll honor it in the spring.