WindBorne Systems, a Redwood Shores, CA-based operator of a global constellation of autonomous weather balloons that collects atmospheric data to power AI weather forecasts, has raised $37 million in Series B funding co-led by Khosla Ventures and Galvanize Climate Solutions. The company operates hundreds of long-duration smart balloons that generate 30x more vertical atmospheric profiles than traditional radiosondes. The capital will scale its Atlas balloon constellation and WeatherMesh AI forecasting models.
AI Weather Models Reshape Forecasting
The timing comes amid rapid investment in AI-driven weather intelligence. Tomorrow.io raised $210M Series F in February 2026 while Sofar Ocean secured $39M Series B. WindBorne's approach combines proprietary in-situ balloon data with transformer-based models that update every 20 minutes, addressing the gap where 85% of Earth's atmosphere remains under-observed.
Balloon Data Closes Atmospheric Gaps
Traditional observation networks leave massive blind spots over oceans and developing regions. WindBorne balloons fly for 40+ days on average, delivering real-time temperature, pressure, humidity, and wind data that is already assimilated into NOAA's Global Forecast System. This data has improved hurricane track predictions by up to 18% according to NOAA findings.
WeatherMesh Outperforms Physics Models
WindBorne's WeatherMesh-6 model beats ECMWF's IFS and Google DeepMind benchmarks across all variables and lead times from 1-10 days while running 100,000x faster than traditional numerical weather prediction. The company also launched MetaMesh, a multi-model blend that incorporates its proprietary data.
As John Dean, CEO, noted:
"We demonstrated that when you add balloons to the forecast, you get more accurate forecasts, and the value per data point is much stronger than satellites."
Khosla and Galvanize Co-Lead Round
Khosla Ventures, which led the prior $15M Series A, doubled down alongside climate-focused Galvanize Climate Solutions. Lux Capital and TransLink Capital also participated. The round signals strong conviction in hardware-plus-AI infrastructure for energy trading, utilities, and government forecasting.
Weather Intelligence Market Expands
The global weather forecasting services market stands at $2.95B and is projected to reach $5.23B by 2034 per Fortune Business Insights. AI-based weather modelling is forecast to grow from $235M to $926M by 2033 at 21.3% CAGR per Grand View Research. Competitors include Meteomatics with $22M Series C in January 2025 and Brightband, which raised $10M Series A in September 2024.
Scaling to 10,000 Balloons
WindBorne has tripled both revenue and its balloon constellation in the past year, now operating more than 600 balloons from 20 global launch sites. The company is expanding manufacturing capacity toward 10,000 concurrent balloons, the benchmark for adequate global coverage.