Pool swim season in Mercedes, TX
When can you swim in an outdoor pool in Mercedes, TX?
An unheated pool in Mercedes reaches 78°F in May to Oct, about 6 months a year. The air allows up to 12 swimmable months with a heater (all year).
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What each heater buys you in Mercedes
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 6 | May to Oct | $0 | $0 |
| Solar cover only | 8 | Apr to Nov | $0 | $50 |
| Solar panels + cover | 9 | Mar to Nov | $0 | $283 |
| Heat pump + cover | 12 | all year | $356 | $906 |
| Gas heater + cover | 12 | all year | $847 | $1,272 |
For a 450 sq ft pool held at 80°F, at TX prices of 16.0¢/kWh electricity and $19/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Mercedes
Heat pump + cover: 12 of 12 possible months for about $906 a year all-in, which works out near $151 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: Weslaco, 4 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Mercedes 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 | 71° | 61° | 3.1 | 61° | 67° | $124 | $285 |
| Feb | 75° | 64° | 3.7 | 63° | 69° | $100 | $242 |
| Mar | 81° | 70° | 4.6 | 69° | 75° | $43 | $112 |
| Apr | 86° | 76° | 5.4 | 75° | 81° | – | – |
| May | 90° | 81° | 6.0 | 81° | 87° | – | – |
| Jun | 95° | 85° | 6.5 | 87° | 93° | – | – |
| Jul | 96° | 86° | 6.5 | 89° | 95° | – | – |
| Aug | 97° | 87° | 6.2 | 90° | 96° | – | – |
| Sep | 92° | 82° | 5.2 | 87° | 93° | – | – |
| Oct | 87° | 77° | 4.6 | 81° | 87° | – | – |
| Nov | 80° | 69° | 3.5 | 73° | 79° | $5 | $13 |
| Dec | 72° | 62° | 2.8 | 65° | 71° | $84 | $195 |
Heating costs most in Jan (about $124 with a heat pump, $285 with gas). Sunshine peaks in Jun at 6.5 kWh/m²/day (NASA satellite data, 56.3 km grid cell). Highlighted months are swimmable with no heater.
How Mercedes compares with nearby cities
Mercedes ranks 18 of 252 Texas cities for unheated swim months; Alamo, San Juan nearby get a longer season without a heater.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Weslaco, TX | 5 mi | 6 | 12 | $356 |
| Donna, TX | 8 mi | 6 | 12 | $349 |
| Alamo, TX | 13 mi | 7 | 12 | $254 |
| Harlingen, TX | 14 mi | 6 | 12 | $323 |
| San Juan, TX | 15 mi | 7 | 12 | $254 |
| San Benito, TX | 17 mi | 6 | 12 | $323 |