If you plan to raise flowers, herbs, vegetables, or fruiting plants year round, I highly suggest you invest in a good greenhouse that will not only provide protection for your plants, but also protects you against the environment while you tend your plants.
Make sure the structure is safe and sturdy. There are greenhouses on the market that will do fine in calm days, or in areas where there is no heavy snow or harsh sun beating on them. Put the same structure in a decent Santa Ana wind and you will see them rattle, shake, and fall apart in a hurry. There are good DIY plans out there that will meet your needs, and your safety requirements.