SwimSeasonCheck

When can I swim in my pool, and do I need a heater?

Type your city. You get the months an outdoor pool is warm enough without a heater, what each kind of heater adds, and what that costs at your state's energy prices.

Water temperature is an estimate from 30 years of NOAA air normals and NASA sunshine data, not a reading from a real pool. Shade, wind and pool depth move it by a few degrees.

What you get back: the months an outdoor pool stays at 78°F or warmer, unheated and with a heat pump.
Phoenix, AZ
Unheated
  1. J
  2. F
  3. M
  4. A
  5. M
  6. J
  7. J
  8. A
  9. S
  10. O
  11. N
  12. D
6
Heat pump
  1. J
  2. F
  3. M
  4. A
  5. M
  6. J
  7. J
  8. A
  9. S
  10. O
  11. N
  12. D
9
Los Angeles, CA
Unheated
  1. J
  2. F
  3. M
  4. A
  5. M
  6. J
  7. J
  8. A
  9. S
  10. O
  11. N
  12. D
0
Heat pump
  1. J
  2. F
  3. M
  4. A
  5. M
  6. J
  7. J
  8. A
  9. S
  10. O
  11. N
  12. D
8
Chicago, IL
Unheated
  1. J
  2. F
  3. M
  4. A
  5. M
  6. J
  7. J
  8. A
  9. S
  10. O
  11. N
  12. D
0
Heat pump
  1. J
  2. F
  3. M
  4. A
  5. M
  6. J
  7. J
  8. A
  9. S
  10. O
  11. N
  12. D
4

Each city page tells you

The months you can swim with no heater
Estimated water temperature month by month, against 78°F.
What a cover, solar panels, a heat pump or gas actually add
In months, and in dollars at your state's real electricity and gas prices.
Whether to buy one at all
In some places a heater adds one month for a four-figure bill. The page says so.