# Data Dictionary - US Heating & Cooling Degree Days by Region - daily, base 18 °C, cleaned Parquet

**Units:** vary by `metric` - read the per-row `unit` column (overall: degree-days).  Times are UTC.

| column | type | description |
|---|---|---|
| `zone` | str | US power-market region code |
| `ts` | timestamp (UTC) | Day |
| `metric` | str | Heating degree days / Cooling degree days |
| `value` | float | Degree-days (base 18 °C) |
| `unit` | str | Unit |
| `res_min` | int | Native resolution (daily = 1440) |

*Source: NASA POWER Project (NASA Langley Research Center).*