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PurpleAir vs Weather Underground

PurpleAir logo

PurpleAir

Weather

Real-time air quality monitoring for communities

From
$229/one-time
Rated
-
Full reviewWebsite
Weather Underground logo

Weather Underground

Weather

Crowdsourced hyperlocal weather from personal stations

From
Free
Rated
-
Full reviewWebsite

The short version

  • Only Weather Underground has a free tier, so it costs nothing to try first.
  • Each has a real cost: PurpleAir purpleAir sensors are one-time hardware purchases rather than a subscription, priced $199 to $279 USD per unit for named models (PA-I-Indoor, PA-II, PA-II-SD), per the vendor's own store (archived, 2021).; Weather Underground free public API discontinued as of December 31, 2018 with no new developer accounts accepted
  • They diverge on capability: PurpleAir covers PM2.5 monitoring, Weather Underground covers Personal weather stations.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which PurpleAir and Weather Underground actually diverge.

Attributes where PurpleAir and Weather Underground differ
AttributePurpleAirWeather Underground
Starting price$229/one-timeFree
Pricing modelone-timefreemium
Free tierNoYes
PlatformsWeb, Api, HardwareWeb, Mobile web, Personal Weather Station network
Founded20152003

Identical on both: user rating (Not yet rated), category (Weather).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in PurpleAir

  • PM2.5 monitoring
  • Real-time map
  • Historical data
  • Community network
  • API access
  • API access
  • Home Assistant
  • Data downloads

Only in Weather Underground

  • Personal weather stations
  • Hyperlocal data
  • Historical records
  • Webcams
  • Community forums
  • PWS networks
  • Smart home
  • APIs

Both cover

  • Web support

What people use each for

The jobs each tool is most often brought in to do.

PurpleAir

  • Professional Work
  • Content Creation

Weather Underground

  • Professional Work
  • Content Creation

Both are used for professional work, content creation, on those jobs the choice comes down to price and fit rather than capability.

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

PurpleAir

  • PurpleAir sensors are one-time hardware purchases rather than a subscription, priced $199 to $279 USD per unit for named models (PA-I-Indoor, PA-II, PA-II-SD), per the vendor's own store (archived, 2021).

Weather Underground

  • Free public API discontinued as of December 31, 2018 with no new developer accounts accepted
  • Previous enterprise pricing was expensive at $150/month for Cumulus Drizzle plan
  • No longer competitive for developers needing reliable weather API access
  • Service is in wind-down phase with limited future development

Pricing, plan by plan

PurpleAir

$229/one-time
  • Outdoor Sensor$229/one-time
    • PM2.5 monitoring
    • Cloud connectivity
    • Map access
  • Indoor Sensor$199/one-time
    • Indoor monitoring
    • WiFi enabled
    • Real-time data

Weather Underground

Free
  • FreeFree
    • PWS data access
    • Forecasts
    • Historical data
  • Ad-Free$1.99/month
    • No advertisements
    • Premium features

Which should you pick?

Choose PurpleAir if

  • You need pm2.5 monitoring.
  • You work on Web, Api, Hardware.
  • You also want real-time map.
PurpleAir review

Choose Weather Underground if

  • You need personal weather stations.
  • You want to start without paying.
  • You work on Web, Mobile web, Personal Weather Station network.
  • You also want hyperlocal data.
Weather Underground review

Questions people ask

Is PurpleAir or Weather Underground better?
Neither clearly leads. PurpleAir starts at $229/one-time and Weather Underground at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, PurpleAir or Weather Underground?
Weather Underground has a free tier; the other does not. Paid plans start at $229/one-time for PurpleAir and Free for Weather Underground.
Does PurpleAir or Weather Underground run on more platforms?
PurpleAir runs on Web, Api, Hardware. Weather Underground runs on Web, Mobile web, Personal Weather Station network.
Can I use Weather Underground for free?
Yes. Weather Underground has a free tier, so you can try it without paying. PurpleAir starts at $229/one-time.
What is PurpleAir best used for?
PurpleAir is most often used for professional work, content creation.
What can PurpleAir do that Weather Underground cannot?
PurpleAir covers PM2.5 monitoring, Real-time map, Historical data, Community network. Weather Underground covers Personal weather stations, Hyperlocal data, Historical records, Webcams. Both handle Web support.

Answered from the vendors’ own pages

Weather Underground: What happened to the Weather Underground API?

The free public API was discontinued on December 31, 2018, after IBM acquired The Weather Company. The service is now in a wind-down phase with no new developer accounts accepted.

Source
Weather Underground: Can I still use Weather Underground's data?

Free API keys are still available for Personal Weather Station (PWS) owners who upload data to the network. General developers need to migrate to alternative weather API providers.

Source
Weather Underground: What was the pricing for Weather Underground's Cumulus plans?

The Cumulus Drizzle plan cost $150/month, which many developers found prohibitively expensive for weather data compared to modern alternatives.

Source
Weather Underground: Does Weather Underground still offer a consumer-facing service?

Yes. The consumer website continues to provide weather forecasts, news, alerts, and access to personal weather station data through the PWS network.

Source
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