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Overview

The DeltaDaemon API provides programmatic access to historical NWS forecast accuracy data for US weather stations. Quantify forecast bias, reliability, and error distributions by location, lead time, date range, and weather regime. Health and station metadata are public; data and accuracy endpoints require a session cookie (browser) or Authorization: Bearer <API key>. Rate limits apply per plan; 401 if unauthenticated, 402 if plan is past_due or cancelled.

← How to Work with Delta Daemon

Response Format →

cURL

# Base URL
https://api.deltadaemon.com/api/v1

# API Key (get one at https://deltadaemon.com/signin)
export API_KEY="your_api_key"

# Data Sources
# - Forecasts: NWS gridpoint hourly forecasts via api.weather.gov
# - Observations: NWS ASOS/AWOS automated station observations
# - Daily maxima: midnight-to-midnight local time (NWS CLI methodology)

# Temperature Convention
# - All temperatures in Fahrenheit (use temp_unit=celsius to convert)
# - Daily max = highest observed temp during station local calendar day
# - Accuracy endpoints: optional metric=high (default) or metric=low (forecast_low vs daily min)

# Error Convention
# - error = forecast - observed
# - Positive error = forecast too warm (over-prediction)
# - Negative error = forecast too cool (under-prediction)

# Date Parameters
# - days: rolling window (today minus N days)
# - date_from / date_to: explicit window (overrides days)
# - forecast_for_date: which day the forecast applies to

cURL

# Base URL
https://api.deltadaemon.com/api/v1

# API Key (get one at https://deltadaemon.com/signin)
export API_KEY="your_api_key"

# Data Sources
# - Forecasts: NWS gridpoint hourly forecasts via api.weather.gov
# - Observations: NWS ASOS/AWOS automated station observations
# - Daily maxima: midnight-to-midnight local time (NWS CLI methodology)

# Temperature Convention
# - All temperatures in Fahrenheit (use temp_unit=celsius to convert)
# - Daily max = highest observed temp during station local calendar day
# - Accuracy endpoints: optional metric=high (default) or metric=low (forecast_low vs daily min)

# Error Convention
# - error = forecast - observed
# - Positive error = forecast too warm (over-prediction)
# - Negative error = forecast too cool (under-prediction)

# Date Parameters
# - days: rolling window (today minus N days)
# - date_from / date_to: explicit window (overrides days)
# - forecast_for_date: which day the forecast applies to