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Solar Panels at 115 Degrees: How Arizona Heat Affects Output

At 115 degrees, solar panels still make power. The number people see on a weather app is air temperature, and it is not the same as the temperature of the cells on your roof or the maximum temperature a panel is rated to handle. More sun is not the same as more output. Heat lowers a panel's efficiency, so the hottest afternoon is rarely your best production hour.

Updated Oct 22, 2026

Heat lowers solar panel output

Three different temperatures get mixed together in searches about 115 degrees:

  • Air temperature: what the thermometer reads, such as 115°F.
  • Cell or surface temperature: how hot the panel itself runs, which is well above the air temperature on a sunny roof.
  • Rated operating limit: the maximum a panel is built to tolerate, which is far higher than typical air temperatures.

Panels are rated at standard test conditions of 77°F (25°C) cell temperature. A hot roof means output falls below the nameplate number during peak afternoon hours.

Rooftop solar array under bright sun
A rooftop solar array in strong sun

Production dips, but it does not stop.

The number to compare between panels is the temperature coefficient on the spec sheet. A less-negative value means less output lost for each degree of heat. No numbered source on this page supplies a coefficient range or a percentage loss for Arizona roofs, so use the figure printed on the specific panel's datasheet.

Ask your installer to model production with desert heat rather than the nameplate rating alone. Also ask how much air gap will sit between the array and the roof, since ventilation helps panels shed heat.

Decide

Which temperature are you reading?

What does the number describe?

  • If The thermometer reading, such as 115°F

    then: Air temperature

  • If How hot the panel itself runs

    then: Cell or surface temperature

  • If The most a panel is built to tolerate

    then: Rated operating limit

Dirt and shading can make hot spots worse, so a clean array matters more in summer.

How many days a year reach 100 degrees, by county

The table shows the average number of days a year at or above 100°F. Figures are based on NOAA 1991-2020 climate normals from a single station in each county, not a county average.

County Station Days at or above 100°F
Yuma Yuma Mcas 118.2[15]
Pinal Casa Grande Nm 115.6[12]
Maricopa Phoenix Sky Harbor International Airport 111.3[8]
La Paz Parker 126.3[7]
Pima Tucson International Airport 67.9[11]
Graham Safford Ag Ctr 45.6[5]
Greenlee Duncan 40.2[6]
Mohave Kingman Mohave Co Airport 32.4[9]
Gila Globe #3 31.2[4]
Santa Cruz Nogales 6 N 22.3[13]
Navajo Winslow Muni Airport 12.3[10]
Apache Saint Johns 1.2[1]
Yavapai Prescott 1.2[14]
Cochise Bisbee 1Wnw 0.3[2]
Coconino Flagstaff Pulliam Airport 0.0[3]

La Paz County is the hottest on these rows, and Coconino County is the coolest. Read the count as a rough measure of how often heat trims output, not as a verdict on whether solar is worthwhile.

126.3

days a year at or above 100°F at the Parker station in La Paz County

Duncan is 23 miles from the Greenlee County seat, and Winslow is 34 miles from the Navajo County seat. For more climate rows, see Arizona temperature and monsoon rain by county.

What heat means for panel lifespan

The heat-related dip in output on a hot afternoon is temporary, and it eases as the panel cools.

Long-term effects are a different question.

None of the numbered sources on this page covers degradation rates or warranty terms, so this page states no lifespan figure. Compare the warranty and degradation terms printed in each manufacturer's documentation instead.

Ask the installer to inspect for hotspots, loose connections and heat-exposed equipment after a long heat wave or a monsoon storm.

Choose a licensed installer

Heat performance belongs on your list of questions for an installer: temperature coefficient, air gap, and a production estimate built for desert conditions.

The solar hub covers the license classes that apply to solar work, and solar permit rules by city show where a permit applies.

Before you sign, check the contractor's Arizona license so you know the license on file matches the work.

Quick answers

Do solar panels stop working at 115 degrees?

No. Production dips on a hot roof during peak afternoon hours, but it does not stop.

Is 115°F the panel temperature?

Not usually. 115°F is air temperature, and the panel's cell temperature runs well above it on a sunny roof.

What number should I compare between panels?

The temperature coefficient on the datasheet. A less-negative value means less output lost for each degree of heat.

Sources

  1. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Saint Johns (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USC00027435&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  2. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Bisbee 1Wnw (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USC00020775&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  3. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Flagstaff Pulliam Airport (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USW00003103&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  4. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Globe #3 (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USC00023501&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  5. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Safford Ag Ctr (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USC00027390&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  6. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Duncan (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USC00022754&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  7. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Parker (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USC00026250&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  8. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Phoenix Sky Harbor International Airport (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USW00023183&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  9. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Kingman Mohave Co Airport (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USW00093167&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  10. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Winslow Muni Airport (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USW00023194&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  11. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Tucson International Airport (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USW00023160&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  12. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Casa Grande Nm (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USC00021314&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  13. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Nogales 6 N (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USC00025924&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  14. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Prescott (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USC00026796&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.
  15. NOAA National Centers for Environmental Information. "NOAA 1991-2020 Climate Normals, Yuma Mcas (annual days at or above 100 F)." https://www.ncei.noaa.gov/access/services/data/v1?includeStationName=1&format=csv&stations=USW00003145&dataset=normals-annualseasonal-1991-2020&dataTypes=ANN-TMAX-AVGNDS-GRTH100. Accessed October 21, 2026.