Nah, radishes are 'cool growers' Ken. I used to plant them in Utah in March, and the seedlings would survive even a late snow or two in April. Most places they are planted along with the peas, lettuce, carrots and cabbage-y things.
Here in FL, if I waited to plant them at the same time as the warm growers, tomatoes and peppers, (end of Feb), they'd be woody little golf balls by the time they were ready to harvest in April-ish.
