I have some pots with geranium in my garden.
Since where I live winter comes with some frost and snow, I have already confirmed that leaving the geranium in the garden will make them not survive the winter.
So far I always brought the pots inside to winter, but for logistic reason I would prefer leaving them outside.
Would storing the pots below a garden table be sufficient to protect the geranium from frost/snow damage?
On the assumption you're using the common term 'geranium' for pelargonium, how cold and wet your winters actually are is a big factor in deciding whether you can keep them alive outdoors. If temperatures frequently fall below zero degrees C and stay there night and day for longer than 5 days, the pots will freeze and all will die. Equally, somewhere with excessively wet winters significantly reduces the chances of their surviving outdoors.
I live in the south of the UK, and I overwinter my pelargoniums outdoors in winter, BUT, its a risk - we generally have relatively mild winters, but in a particularly cold one, they die. The last time that happened here was in 2010, so I have an ivy leaved pelargonium on my balcony which is now 6 feet tall and 3 feet wide, grown up a support against a wall, which has been there since 2011. It is under a half 'ceiling' at the top of my balcony, in a corner so it is well protected on two sides, and very little rain gets to it. Last December, when I put up my outdoor lights for Christmas, it looked rather incongruous - this pelargonium was still covered in pink flowers, and the combination of Christmas lights and flowers looked a bit odd! It may look rather tatty as the winter progresses, so usually in early March, I tidy it up, cutting back as necessary to healthier parts.
These plants will tolerate up to ten degrees of frost for short periods, but what they won't tolerate is the combination of wet and cold. Damp weather in winter is pretty deadly because the pelargoniums succumb to fungal infection and that's what kills them. In parts of Europe with generally dry winters, pelargoniums survive quite well outdoors despite some exposure to cold temperatures.
The trick is to keep them out of the rain in as sheltered a place as possible; under your garden table probably won't work unless you push it against a warm house wall, because the best place is against the house wall, in a south facing position, with some sort of shelter over the top of them to keep the rain off. With the exception of the large ivy leafed pelargonium, which is in a pot 2 feet deep, I usually cut down the smaller ones to about 3/4 inches in height, removing any leaf debris from the top of the soil and stand them, in pots, on a southfacing windowsill outside, which means they are under a bit of a ceiling to my balcony, though they do still get some rain at times when the wind is from the south, unfortunately. It is important to check them regularly to remove any dead bits or leaves from the top of the soil and the plants to reduce the risk of fungal infection. Most make it through, some don't.
The other thing you can try is to find a pot large enough to house all the Pelargoniums you have, cut them all back to 3-4 inches, remove from whatever they're in currently, shaking off soil from the roots, and crowd them all in together in one pot or container, in potting soil, and keep that somewhere very sheltered and out of the rain. This can work, although sometimes the ones at the edges nearest the front of the shelter don't make it.
Note that those plants known as Regal Pelargoniums (Pelargonium grandiflorum) are unlikely to survive outdoors in winter; they seem to be more sensitive.
Some frost and snow will kill the Pelargonium type geranium. The problem is many varieties are covered in small hairs which transmits the cold into the leaves and stems, ruptures cell walls and rot quickly sets in. They are not adapted to cold at all. But they are adapted to drought. They come from the deserts of Southern Africa where they regularly dry out in drought and spring back to life in plentiful rains. So your solution, if you have a cool place to store them even in a cupboard, is to shake off all the soil from the roots and dry them out thoroughly. Then re-pot in spring, water, and they will spring back to life.
Many people hang them in bunches in a cool airy room while they go on holiday for months in winter, then have their "geraniums" back in flower in no time on return. No worries about watering or lack of light, just following the routine that geraniums know very well.
