Energy / Degree Day Forecast API

Energy-focused forecast endpoint including degree-day and irradiance used for energy and load planning.

API Guide

Energy / Degree Day Forecast API

Energy-focused forecast endpoint including degree-day and irradiance used for energy and load planning.

Returns both weather and energy-relevant forecast fields.

Frequently Asked Questions

How are heating and cooling degree days calculated?

Degree days estimate heating or cooling demand relative to a selected temperature threshold. We calculate HDD and CDD from hourly temperature values, which better captures intraday swings than a simple daily max/min average.

Read blog post

What does the `solar_rad` field represent?

The solar radiation field is an estimated surface solar flux value that accounts for cloud cover, surface albedo, and atmospheric effects. Alternatively, GHI/DNI/DHI values are clear-sky values which do not account for these.

Read help article

Request Parameters

Field Optional/Required Type Data Type Description
lat Required query number Latitude component of location.
lon Required query number Longitude component of location.
threshold Optional query number Temperature threshold to use to calculate degree days (default 18 C)
units Optional query string Convert to units. Default Metric. Options (I = Imperial, M = Metric, S = Scientific) Options: S, I, M
tp Optional query string Time period (default: daily) Options: hourly, daily
key Required query string Your registered API key.

Example Request

Geolocation options: lat/lon (recommended)

Enter API key

lat/lon (recommended)

https://api.weatherbit.io/v2.0/forecast/energy?key=API_KEY&lat=35.7796&lon=-78.6382
curl -s "https://api.weatherbit.io/v2.0/forecast/energy?key=API_KEY&lat=35.7796&lon=-78.6382"
require 'uri'
require 'net/http'
require 'json'

uri = URI("https://api.weatherbit.io/v2.0/forecast/energy?key=API_KEY&lat=35.7796&lon=-78.6382")
http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl = (uri.scheme == "https")
request = Net::HTTP::Get.new(uri)
response = http.request(request)
json = JSON.parse(response.body)
puts JSON.pretty_generate(json)
const https = require("https");

https.get("https://api.weatherbit.io/v2.0/forecast/energy?key=API_KEY&lat=35.7796&lon=-78.6382", (res) => {
  let raw = "";
  res.on("data", (chunk) => { raw += chunk; });
  res.on("end", () => {
    const json = JSON.parse(raw);
    console.log(JSON.stringify(json, null, 2));
  });
}).on("error", (err) => {
  console.error(err.message);
});
Estimated quota: 1 requeststandard

Example Response HTTP 200

{
  "city_name": "Phoenix",
  "country_code": "US",
  "data": [
    {
      "cdd": 9.566042,
      "clouds": 1,
      "date": "2026-06-02",
      "dewpt": -3.3088942,
      "hdd": 0,
      "max_wind_spd": 10.703125,
      "max_wind_spd_100m": 12.980885,
      "precip": 0,
      "rh": 8,
      "snow": 0,
      "sun_hours": 6.2231994,
      "t_dhi": 903.12,
      "t_dni": 7123.75,
      "t_ghi": 6223.2,
      "t_solar_rad": 6223.199,
      "temp": 35.990383,
      "temp_wetbulb": 16.028856,
      "timestamp_local": null,
      "timestamp_utc": null,
      "wind_dir": 278,
      "wind_dir_100m": 267,
      "wind_spd": 4.6088557,
      "wind_spd_100m": 6.522531
    },
    {
      "cdd": 15.016666,
      "clouds": 3,
      "date": "2026-06-03",
      "dewpt": -0.83658487,
      "hdd": 0,
      "max_wind_spd": 5.4,
      "max_wind_spd_100m": 9.5176935,
      "precip": 0,
      "rh": 12,
      "snow": 0,
      "sun_hours": 8.598942,
      "t_dhi": 1330.8201,
      "t_dni": 10653.84,
      "t_ghi": 8598.99,
      "t_solar_rad": 8598.935,
      "temp": 33.34667,
      "temp_wetbulb": 15.441433,
      "timestamp_local": null,
      "timestamp_utc": null,
      "wind_dir": 218,
      "wind_dir_100m": 232,
      "wind_spd": 1.7833333,
      "wind_spd_100m": 3.9319463
    },
    {
      "cdd": 15.222083,
      "clouds": 2,
      "date": "2026-06-04",
      "dewpt": 0.39336398,
      "hdd": 0,
      "max_wind_spd": 7.8,
      "max_wind_spd_100m": 11.017624,
      "precip": 0,
      "rh": 13,
      "snow": 0,
      "sun_hours": 8.606662,
      "t_dhi": 1331.53,
      "t_dni": 10659.79,
      "t_ghi": 8606.67,
      "t_solar_rad": 8383.004,
      "temp": 33.552082,
      "temp_wetbulb": 15.858048,
      "timestamp_local": null,
      "timestamp_utc": null,
      "wind_dir": 199,
      "wind_dir_100m": 210,
      "wind_spd": 2.3233333,
      "wind_spd_100m": 4.3713956
    },
    {
      "cdd": 14.674167,
      "clouds": 1,
      "date": "2026-06-05",
      "dewpt": 0.20331913,
      "hdd": 0,
      "max_wind_spd": 7.6,
      "max_wind_spd_100m": 14.629183,
      "precip": 0,
      "rh": 13,
      "snow": 0,
      "sun_hours": 8.613829,
      "t_dhi": 1332.24,
      "t_dni": 10665.29,
      "t_ghi": 8613.83,
      "t_solar_rad": 8395.945,
      "temp": 33.004166,
      "temp_wetbulb": 15.588694,
      "timestamp_local": null,
      "timestamp_utc": null,
      "wind_dir": 222,
      "wind_dir_100m": 246,
      "wind_spd": 3.1095834,
      "wind_spd_100m": 6.2135878
    },
    {
      "cdd": 14.012917,
      "clouds": 11,
      "date": "2026-06-06",
      "dewpt": 1.8923435,
      "hdd": 0,
      "max_wind_spd": 7.6,
      "max_wind_spd_100m": 11.364197,
      "precip": 0,
      "rh": 15,
      "snow": 0,
      "sun_hours": 8.6163645,
      "t_dhi": 1332.85,
      "t_dni": 10670.32,
      "t_ghi": 8620.45,
      "t_solar_rad": 8367.236,
      "temp": 32.34292,
      "temp_wetbulb": 15.826333,
      "timestamp_local": null,
      "timestamp_utc": null,
      "wind_dir": 205,
      "wind_dir_100m": 205,
      "wind_spd": 3.83125,
      "wind_spd_100m": 4.6465883
    },
    {
      "cdd": 15.114011,
      "clouds": 93,
      "date": "2026-06-07",
      "dewpt": 1.0086149,
      "hdd": 0,
      "max_wind_spd": 8.8125,
      "max_wind_spd_100m": 10.90621,
      "precip": 0,
      "rh": 14,
      "snow": 0,
      "sun_hours": 3.4776783,
      "t_dhi": 1272.78,
      "t_dni": 10111.74,
      "t_ghi": 8622.54,
      "t_solar_rad": 1537.4442,
      "temp": 32.447918,
      "temp_wetbulb": 15.582192,
      "timestamp_local": null,
      "timestamp_utc": null,
      "wind_dir": 244,
      "wind_dir_100m": 218,
      "wind_spd": 3.565484,
      "wind_spd_100m": 4.5209165
    },
    {
      "cdd": 15.015703,
      "clouds": 2,
      "date": "2026-06-08",
      "dewpt": 0.81759644,
      "hdd": 0,
      "max_wind_spd": 8.1015625,
      "max_wind_spd_100m": 9.825677,
      "precip": 0,
      "rh": 13,
      "snow": 0,
      "sun_hours": 8.626628,
      "t_dhi": 1272.9,
      "t_dni": 10111.68,
      "t_ghi": 8626.65,
      "t_solar_rad": 8394.837,
      "temp": 33.345703,
      "temp_wetbulb": 15.940627,
      "timestamp_local": null,
      "timestamp_utc": null,
      "wind_dir": 198,
      "wind_dir_100m": 263,
      "wind_spd": 3.6300633,
      "wind_spd_100m": 4.4025865
    },
    {
      "cdd": 15.871172,
      "clouds": 1,
      "date": "2026-06-09",
      "dewpt": -0.77789307,
      "hdd": 0,
      "max_wind_spd": 7.1992188,
      "max_wind_spd_100m": 8.731303,
      "precip": 0,
      "rh": 12,
      "snow": 0,
      "sun_hours": 8.6304,
      "t_dhi": 1272.99,
      "t_dni": 10111.53,
      "t_ghi": 8630.399,
      "t_solar_rad": 8630.399,
      "temp": 34.20117,
      "temp_wetbulb": 15.911085,
      "timestamp_local": null,
      "timestamp_utc": null,
      "wind_dir": 268,
      "wind_dir_100m": 241,
      "wind_spd": 2.985981,
      "wind_spd_100m": 3.6214354
    }
  ],
  "lat": 33.4484,
  "lon": -112.074,
  "state_code": "AZ",
  "threshold_units": "C",
  "threshold_value": 18.33,
  "timezone": "America/Phoenix"
}

HTTP Statuses

Code Description Example
200 An Energy Data Object. -
204 No Data Found -
400 Client Error 
{
  "error": "Some relevant message"
}
403 Unauthorized/No Access for current plan level 
{
  "error": "Some relevant message"
}
429 Daily or Velocity limit exceeded See rate limit guidance. 
{
  "error": "Rate limit exceeded.",
  "status_code": 429,
  "status_message": "Rate limit exceeded. Try again later."
}
500 Internal Server Error 
{
  "error": "Server Error"
}

Return Fields

Field Data Type Description
city_name string Nearest city name
state_code string State abbreviation
country_code string Country abbreviation
timezone string Local IANA time zone
lat number Latitude
lon number Longitude
threshold_units string Degree day threshold units
threshold_value string Degree day threshold
data array<EnergyForecastSeries>
data[].date string Date
data[].timestamp_local ['string', 'null'] Timestamp in local time
data[].timestamp_utc ['string', 'null'] Timestamp UTC
data[].cdd number Cooling degree days
data[].hdd number Heating degree days
data[].rh integer Average Relative humidity (%)
data[].dewpt number Average dew point temperature - Default (C)
data[].max_wind_dir integer Average max 10m wind direction (Degrees) - Degrees clockwise from 0 = North
data[].max_wind_dir_100m integer Average max wind direction at 100m height (Degrees) - Degrees clockwise from 0 = North
data[].max_wind_spd number Max 10m wind speed - Default (m/s)
data[].max_wind_spd_100m number Max wind speed at 100m height - Default (m/s)
data[].wind_dir integer Average wind direction (Degrees) - Degrees clockwise from 0 = North
data[].wind_dir_100m integer Average wind direction at 100m height (Degrees) - Degrees clockwise from 0 = North
data[].wind_spd number Average wind speed at 10m height - Default (m/s)
data[].wind_spd_100m number Average wind speed at 100m height - Default (m/s)
data[].temp number Average temperature - Default (C)
data[].temp_wetbulb number Average wetbulb temperature - Default (C)
data[].clouds integer Average cloud cover (%)
data[].t_ghi number Total clear sky global horizontal solar irradiance (W/m^2)
data[].t_dhi number Total clear sky diffuse horizontal solar irradiance (W/m^2)
data[].t_dni number Total clear sky direct normal solar irradiance (W/m^2)
data[].t_solar_rad number Total solar radiation (W/m^2) - Accounts for cloud cover, and other factors.
data[].sun_hours number Average number of daily sun hours - # hours where Solar GHI > 1000 W/m^2
data[].precip number Total precipitation in period - Default (mm)
data[].snow number Total snowfall in period - Default (mm)
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