Pool swim season in Lake Forest, CA
When can you swim in an outdoor pool in Lake Forest, CA?
An unheated pool in Lake Forest reaches 78°F in Aug to Sep, about 2 months a year. The air allows up to 10 swimmable months with a heater (Feb to Nov).
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Heater options for a Lake Forest pool, side by side
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 2 | Aug to Sep | $0 | $0 |
| Solar cover only | 5 | Jun to Oct | $0 | $50 |
| Solar panels + cover | 8 | Apr to Nov | $0 | $283 |
| Heat pump + cover | 10 | Feb to Nov | $857 | $1,407 |
| Gas heater + cover | 10 | Feb to Nov | $1,118 | $1,543 |
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 Lake Forest
Heat pump + cover: 10 of 10 possible months for about $1,407 a year all-in, which works out near $176 for each month it adds.
Before you pay for any heater, buy a solar cover: on its own it adds 3 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: Irvine Rch, 5.3 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Lake Forest 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 | 69° | 59° | 3.2 | 59° | 65° | – | – |
| Feb | 71° | 59° | 4.1 | 60° | 66° | $283 | $354 |
| Mar | 73° | 61° | 5.4 | 63° | 69° | $223 | $288 |
| Apr | 76° | 64° | 6.5 | 66° | 72° | $148 | $198 |
| May | 79° | 67° | 6.9 | 70° | 76° | $79 | $110 |
| Jun | 83° | 71° | 7.3 | 73° | 79° | $12 | $18 |
| Jul | 88° | 75° | 7.4 | 77° | 83° | – | – |
| Aug | 90° | 76° | 7.1 | 80° | 86° | – | – |
| Sep | 89° | 75° | 6.0 | 79° | 85° | – | – |
| Oct | 84° | 71° | 4.6 | 75° | 81° | – | – |
| Nov | 76° | 64° | 3.6 | 68° | 74° | $112 | $150 |
| Dec | 68° | 58° | 2.9 | 61° | 67° | – | – |
Heating costs most in Feb (about $283 with a heat pump, $354 with gas). Sunshine peaks in Jul at 7.4 kWh/m²/day (NASA satellite data, 23.7 km grid cell). Highlighted months are swimmable with no heater.
How Lake Forest compares with nearby cities
Lake Forest ranks 169 of 376 California cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Mission Viejo, CA | 3 mi | 0 | 8 | $738 |
| Laguna Woods, CA | 4 mi | 0 | 8 | $738 |
| Laguna Hills, CA | 5 mi | 0 | 8 | $738 |
| Rancho Santa Margarita, CA | 5 mi | 2 | 10 | $857 |
| Irvine, CA | 6 mi | 1 | 9 | $793 |
| Aliso Viejo, CA | 6 mi | 0 | 8 | $738 |