Climate Design Data Workflow for Washington, DC

Direct answer

NASA POWER's 2001–2020 climatology at the Washington, DC reference point reports an annual mean 2 m temperature of 13.2 °C and relative humidity of 76.5%. The highest monthly maximum is 40.2 °C in July, while the lowest monthly minimum is -18.7 °C in February; these are screening statistics, not code design temperatures. The point response uses LST and the 20-year Meteorological and Solar Monthly & Annual Climatologies (January 2001 - December 2020); its annual corrected precipitation is 3.16 mm/day and annual 10 m wind speed is 3.97 m/s. Use the monthly series to screen source selection before applying project design conditions. NASA POWER is gridded climatology: verify elevation, microclimate, urban exposure, station or weather-file suitability, current code edition and the authority's required source before design use.

Content and cited inputs reviewed by Harth team · Published 2026-08-17 · Updated 2026-08-31.

Which climate inputs control the design?

1. Confirm the project jurisdiction and adopted energy-code edition.
2. Select the authoritative station and record why it applies.
3. Record heating dry-bulb percentiles and cooling dry-bulb with coincident moisture conditions.
4. Keep IP/SI units, edition, observation period and retrieval date with every value.
5. Separate climate-zone envelope requirements from HVAC sizing conditions.

Washington, DC NASA POWER monthly climate screening table

Month-by-month climate interpretation

• January: mean temperature 0.11 °C is 13.04 °C below the annual mean; the monthly max–min span is 37.04 °C. Relative humidity is 81.79% (5.27 points above annual), while corrected precipitation at 2.16 mm/day is 1.00 mm/day drier than the annual daily rate.
• February: mean temperature 1.30 °C is 11.85 °C below the annual mean; the monthly max–min span is 42.08 °C. Relative humidity is 80.45% (3.93 points above annual), while corrected precipitation at 2.49 mm/day is 0.67 mm/day drier than the annual daily rate.
• March: mean temperature 5.83 °C is 7.32 °C below the annual mean; the monthly max–min span is 41.91 °C. Relative humidity is 78.53% (2.01 points above annual), while corrected precipitation at 2.70 mm/day is 0.46 mm/day drier than the annual daily rate.
• April: mean temperature 12.16 °C is 0.99 °C below the annual mean; the monthly max–min span is 36.79 °C. Relative humidity is 76.40% (0.12 points below annual), while corrected precipitation at 3.07 mm/day is 0.09 mm/day drier than the annual daily rate.
• May: mean temperature 17.64 °C is 4.49 °C above the annual mean; the monthly max–min span is 32.47 °C. Relative humidity is 77.95% (1.43 points above annual), while corrected precipitation at 3.53 mm/day is 0.37 mm/day wetter than the annual daily rate.
• June: mean temperature 22.84 °C is 9.69 °C above the annual mean; the monthly max–min span is 28.67 °C. Relative humidity is 74.41% (2.11 points below annual), while corrected precipitation at 3.94 mm/day is 0.78 mm/day wetter than the annual daily rate.
• July: mean temperature 25.79 °C is 12.64 °C above the annual mean; the monthly max–min span is 27.68 °C. Relative humidity is 69.41% (7.11 points below annual), while corrected precipitation at 3.75 mm/day is 0.59 mm/day wetter than the annual daily rate.
• August: mean temperature 25.13 °C is 11.98 °C above the annual mean; the monthly max–min span is 24.57 °C. Relative humidity is 69.68% (6.84 points below annual), while corrected precipitation at 3.53 mm/day is 0.37 mm/day wetter than the annual daily rate.
• September: mean temperature 21.31 °C is 8.16 °C above the annual mean; the monthly max–min span is 29.61 °C. Relative humidity is 71.61% (4.91 points below annual), while corrected precipitation at 3.57 mm/day is 0.41 mm/day wetter than the annual daily rate.
• October: mean temperature 14.40 °C is 1.25 °C above the annual mean; the monthly max–min span is 36.77 °C. Relative humidity is 76.28% (0.24 points below annual), while corrected precipitation at 3.38 mm/day is 0.22 mm/day wetter than the annual daily rate.
• November: mean temperature 7.85 °C is 5.30 °C below the annual mean; the monthly max–min span is 30.95 °C. Relative humidity is 78.83% (2.31 points above annual), while corrected precipitation at 2.67 mm/day is 0.49 mm/day drier than the annual daily rate.
• December: mean temperature 2.75 °C is 10.40 °C below the annual mean; the monthly max–min span is 33.56 °C. Relative humidity is 83.15% (6.63 points above annual), while corrected precipitation at 3.06 mm/day is 0.10 mm/day drier than the annual daily rate.

Harth retrieved this point climatology from NASA POWER API v2.9.7 for location record us:washington-dc. It is a reproducible screening dataset, not an hourly weather file, forecast, code design condition or substitute for local professional review.

Where can you explore related guidance?

• Explore all climate data guidance
• ASHRAE / IECC Climate Zones Explained (Zones 1–8, A/B/C)
• Heating & Cooling Design Temperatures (99%, 1% / 0.4%)
• Climate Design Data Workflow for New York, NY
• Climate Design Data Workflow for Boston, MA
• Sun Path & Solar Angles for Washington, DC

Sources and method

Licensed ASHRAE Climatic Design Information / Standard 169 station data plus the locally adopted energy code. Coordinates 38.9072° N (America/New_York) are approximate routing references. Figures are illustrative — confirm the representative station and current edition. Climate screening data from the NASA POWER Climatology API documentation and exact point response, retrieved 2026-08-31; source period: 20-year Meteorological and Solar Monthly & Annual Climatologies (January 2001 - December 2020). NASA POWER values are gridded screening statistics, not code design conditions or guaranteed local observations.

Source links

• power.larc.nasa.gov

• power.larc.nasa.gov