Growing a watermelon typically takes between 70 and 100 days from planting to harvest, depending on the variety. Smaller varieties like Sugar Baby watermelons mature faster, around 70 to 75 days, while larger varieties may take up to 85-100 days or more

. Key points about watermelon growth duration:

• Average time to maturity: 70–100 days.
• Smaller melons (e.g., Sugar Baby): about 70–75 days.
• Larger melons (e.g., Queen of Hearts): 80–85 days or more.
• Some sources note up to 120 days for certain types under less ideal conditions

Watermelons need warm soil (around 70°F or 21°C) and should be planted after the last frost to avoid cold damage, which slows growth and reduces sweetness

. They require full sun (8–10 hours daily), warm temperatures (70–85°F or 21–29°C), and consistent moisture to reach full size within this timeframe

. In summary, expect about 2.5 to 3.5 months from planting to harvest for most watermelon varieties, with some variation depending on type and growing conditions.