Pool swim season in National City, CA
When can you swim in an outdoor pool in National City, CA?
An unheated pool in National City never reaches 78°F in a normal year. It peaks around 74°F in Aug. The air allows up to 6 swimmable months with a heater (Jun to Nov).
- J
- F
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- D
Heater options for a National City pool, side by side
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 0 | no month | $0 | $0 |
| Solar cover only | 2 | Aug to Sep | $0 | $50 |
| Solar panels + cover | 5 | Jun to Oct | $0 | $283 |
| Heat pump + cover | 6 | Jun to Nov | $456 | $1,006 |
| Gas heater + cover | 6 | Jun to Nov | $619 | $1,044 |
For a 450 sq ft pool held at 80°F, at CA prices of 32.6¢/kWh electricity and $22/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in National City
Solar panels + cover: 5 of 6 possible months for about $283 a year all-in, which works out near $57 for each month it adds.
Before you pay for any heater, buy a solar cover: on its own it adds 2 months here for about $50 a year (why a cover comes first). If you get quotes, ask for a heat pump sized to your pool's surface area; here it beats gas all-in (heat pump or gas).
Weather station: Chula Vista, 1.9 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
National City month by month: air, sun and pool water
| Month | Air high | Air avg | Sun kWh/m²/day | Water, unheated | Water, covered | Heat pump $ | Gas $ |
|---|---|---|---|---|---|---|---|
| Jan | 68° | 57° | 3.2 | 57° | 63° | – | – |
| Feb | 67° | 58° | 4.1 | 58° | 64° | – | – |
| Mar | 67° | 59° | 5.2 | 61° | 67° | – | – |
| Apr | 68° | 61° | 6.1 | 63° | 69° | – | – |
| May | 69° | 63° | 6.1 | 65° | 71° | – | – |
| Jun | 71° | 66° | 5.9 | 68° | 74° | $118 | $163 |
| Jul | 75° | 70° | 6.1 | 71° | 77° | $52 | $76 |
| Aug | 77° | 71° | 6.1 | 74° | 80° | $7 | $11 |
| Sep | 77° | 71° | 5.4 | 73° | 79° | $12 | $18 |
| Oct | 75° | 67° | 4.3 | 70° | 76° | $74 | $103 |
| Nov | 71° | 61° | 3.4 | 64° | 70° | $193 | $248 |
| Dec | 67° | 56° | 2.9 | 59° | 65° | – | – |
Heating costs most in Nov (about $193 with a heat pump, $248 with gas). Sunshine peaks in Apr at 6.1 kWh/m²/day (NASA satellite data, 41.8 km grid cell). Highlighted months are swimmable with no heater.
How National City compares with nearby cities
National City ranks 282 of 376 California cities for unheated swim months; La Mesa nearby gets a longer season without a heater.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Coronado, CA | 3 mi | 0 | 6 | $412 |
| Chula Vista, CA | 6 mi | 0 | 7 | $665 |
| Lemon Grove, CA | 6 mi | 0 | 6 | $456 |
| Imperial Beach, CA | 7 mi | 0 | 5 | $389 |
| La Mesa, CA | 8 mi | 2 | 9 | $834 |
| San Diego, CA | 11 mi | 0 | 8 | $699 |