Summarize:

Most cauliflower varieties require about 1.5-3 months of consistently cool weather to mature properly. Ideally, the daytime temperature while the cauliflower is maturing will be around 60ºF (15.5ºC). This means that the proper planting time depends on your climate:  Cool climates: If your late summer temperatures are below 80ºF (27ºC), you can plant cauliflower for a fall harvest. Start the seeds 8 to 12 weeks before the first fall frost.  Warm climates: If you have frost-free winters, you can plant cauliflower seeds later in autumn, once temperatures have dropped below 80ºF (27ºC). Harvest in winter or early spring.  Temperate climates: Spring-planted cauliflower is difficult to grow in most climates. The coastal valleys of California are the only major exception, and can support year-round crops. Cauliflower is one of the most temperature-sensitive vegetables around. If the temperature requirements above seem difficult to achieve in your area, you can make the job easier with one or more of these tactics:  Look for "summer" or "tropical" varieties that can handle warmer temperatures than most. Wait about a month after the recommended seed-starting date and buy a transplant from a garden store.  Plant a new batch every week for 4–6 weeks to see which works best. Though they require cool weather, paradoxically, cauliflower also require a fair amount of full sun during the day. Choose a spot for planting in your garden that receives full sun and isn't shaded by trees, tall grass, or other crops. You'll also want to make sure that your growing site has ample room for your cauliflower crop. Generally, cauliflower plants will need to be spaced about 18-24 inches apart. For a good cauliflower crop, the plant's growth must be completely uninterrupted. This means that the plant must receive consistent moisture and have access to sufficient nutrients as it matures. A good soil makes meeting both of these requirements much easier. Ideally, your cauliflower's soil should have the following qualities:  High organic matter content. This enhances the soil's ability to hold moisture. High potassium and nitrogen content. Potassium and nitrogen are nutrients vital for the cauliflower's development. If these are not present in the soil, it may be necessary to use fertilizer. A pH of between 6.5 and 7. This "sweet" pH range minimizes the danger of a cauliflower disease called clubroot and maximizes nutrient availability. Cauliflower has a reputation for being somewhat fragile. Many people start with seedlings from a local garden store to transplant into their garden. If you have seeds instead, plant them indoors to protect the young plants from weather:  Plant each seed in its own peat or paper cup. The biodegradable container lets you "plant" the whole pot in your garden later without damaging the cauliflower's roots.  Press the seed about 1/4–1/2 inch (0.6–1.25 cm) deep and cover it with dirt. Water regularly so the soil is moist but not waterlogged. In cold weather, keep the soil at 70º F (21º C) with bottom heat from a warming plate.  If you must plant your seeds directly in the garden, plant them in rows 3 to 6 inches (7.5 to 15 cm) apart. Whether you grew the plants from seed or bought them from a garden nursery, you'll need to move them outdoors once they have three or four true leaves:  Before transplanting, move the seedlings outside for one hour a day. Gradually increase this time over the course of a week to "harden off" the seedlings, adapting them to outdoor conditions. If you used a biodegradable container, bury the container in the ground so the soil level is even with the rest of the garden. If you used a non-biodegradable container, remove the seedling carefully to avoid breaking its roots. Make a small hole in the ground and bury the seedling up to its stem. You may want to make a shallow, saucer-like depression around the seedling to help the surrounding soil retain water. Firm the soil and water the seedling.
Plan to grow cauliflower in cool weather. Adjust to a difficult climate. Choose a growing site with at least six hours of full sun. Start with rich, moisture-retaining soil. Start with transplants or grow seeds indoors. Transplant the seedling.