Sunflowers are tolerant of both hot and cold temperatures, but do better in cooler weather. According to Purdue Extension, sunflower seeds will germinate at temperatures as low as 39 degrees Fahrenheit, but the ideal temperature would be at least 46 to 50 degrees Fahrenheit. The best temperature for growing plants, however, is between 70 to 78 degrees Fahrenheit.
About this Author
Aileen Clarkson has been an award-winning editor and reporter for more than 20 years, earning three awards from the Society of Professional Journalists. She has worked for several newspapers, including "The Washington Post" and "The Charlotte Observer." Clarkson earned a Bachelor of Arts in journalism from the University of Florida.