Source: http://en.wikipedia.org/wiki/Density

Density of liquid water at 1 atm pressure
Temp (°C)[note 1]Density (kg/m3)
100 958.4
80 971.8
60 983.2
40 992.2
30 995.6502
25 997.0479
22 997.7735
20 998.2071
15 999.1026
10 999.7026
4 999.9720
0 999.8395
−10 998.117
−20 993.547
−30 983.854
Notes:
  1. Values below 0 °C refer to supercooled water.