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Caching Best Practices

Although the NWS API doesn't enforce strict rate limits—the exact limit is undisclosed but described as "generous"—applications that rely on the API can significantly improve performance and efficiency by implementing caching best practices. Certain endpoints are updated more frequently than others, and having a caching strategy can reduce the load on the API, decrease response time, and optimize bandwidth usage.

When Should You Cache NWS API Responses?

NWS Endpoint Recommended Caching Time Reason
/alerts/active 5–10 minutes Alerts update frequently but not instantly.
/alerts/active/zone/{zoneId} 5–10 minutes Similar to general alerts, but localized.
/points/{latitude},{longitude}/forecast 15–30 minutes Forecasts update only a few times per day.
/gridpoints/{wfo}/{x},{y}/forecast 15–30 minutes Similar to /points but based on grid data.
/stations/{stationId}/observations/latest 5–10 minutes Weather stations update at different intervals.
/stations/{stationId}/observations 1–2 hours Past observations are static; Don't need real-time fetch.
/zones/{type}/{zoneId} (Zone Metadata) 24 hours Metadata changes very rarely.

How to Implement Caching

1. Using HTTP Headers (Browser & API Clients)

  • The NWS API includes caching headers like:
    • Cache-Control: max-age=600 (600 seconds = 10 minutes)
    • ETag for response versioning
  • Clients can respect these headers instead of re-requesting unchanged data.

2. Local Caching (In-Memory or Database)

  • Store frequently requested API responses in:
    • Redis (fast in-memory store)
    • SQLite/PostgreSQL (for long-term storage)
    • Local JSON files (simple apps)
Click to expand Python example 

import requests
import redis
import json
import time

# Initialize Redis cache
cache = redis.Redis(host='localhost', port=6379, db=0)

def get_forecast(zone_id):
    cache_key = f"forecast:{zone_id}"
    cached_response = cachfor examplet(cache_key)

    if cached_response:
        print("Returning cached data")
        return json.loads(cached_response)

    url = f"https://api.weather.gov/alerts/active/zone/{zone_id}"
    response = requests.get(url, headers={"Accept": "application/json"})

    if response.status_code == 200:
        data = response.json()
        cache.setex(cache_key, 600, json.dumps(data))
        return data

    return None

zone_forecast = get_forecast("NYZ072")
print(zone_forecast)

⏱️ Tip:
- Cache short-lived data (like alerts) for 5–10 minutes
- Cache static data (like zone definitions) for hours or days

Next: Concepts: How Forecasts Are Structured →