🌡️ Now Live on the App Store

Count the heat.
Know your vintage.

The viticulture Growing Degree Day tracker built for wine professionals. Station-accurate GDD for any vineyard, anywhere in the world.

🍎 Download on the App Store See how it works →
🍇 Contra Calor
CURRENT SEASON · 2026
1,842
GDD°F accumulated
WINKLER
II
147
DAYS
38.4°
LAT
84d
LEFT
WINKLER PROGRESS
RIRIIRIIIRIVRV
1.5%
Average variance vs PWS ground truth
3
California wine regions independently validated
Any
Vineyard location in the world supported
Features

Everything a viticulture professional needs.

Built by a Napa Valley wine professional, for the people who live and breathe the growing season.

📍
Pin Any Vineyard
Drop a pin anywhere in the world. Station-priority weather data pulls from NOAA, ASOS, and Weather Underground networks.
🌡️
Winkler Classification
Automatic Region I–V classification using the standard base 50°F formula. Apr 1 – Oct 31, consistent with CIMIS and UC Davis reporting.
📊
Vintage Comparison
Compare up to 3 vintages side by side with accumulation curves aligned from Day 1. Instantly see how this year stacks up.
🍇
Vineyard Profiles
Save multiple vineyard locations with nested vintage history. Load any saved vineyard directly into the tracker in one tap.
🔄
Live Season Tracking
Current season updates automatically each day using delta fetching — only new days are pulled, keeping API usage minimal.
🌏
Both Hemispheres
Full Southern Hemisphere support with harvest year conventions. Oct 1 – Apr 30 season with automatic hemisphere detection.
Validated Accuracy

Independently validated against
CIMIS and Weather Underground.

Site Ground Truth Variance
Napa Valley Floor
vs CIMIS Oakville — 2021		 3,032 GDD +1.8% ✓
Napa Valley Floor
vs CIMIS Oakville — 2015		 3,546 GDD −7.0% ✓
Sierra Foothills
vs PWS Placerville — 2021		 4,346 GDD +1.5% ✓
Sonoma/Bennett Valley
vs CIMIS Bennett Valley — 2021		 2,676 GDD +6.9% ✓

Contra Calor uses Visual Crossing's station-priority weather API — pulling from real physical observation stations closest to your vineyard, not interpolated grid models.

Validated against CIMIS (California Irrigation Management Information System) stations at Oakville and Bennett Valley, and against a Weather Underground personal weather station near Placerville in the Sierra Foothills.

Average variance across validated sites: 3.8% — well within acceptable range for a viticulture decision-support tool.

Read full Data Accuracy Disclaimer →
Pricing

Start free. Upgrade when you're ready.

GDD calculation is always free for any location, any vintage. Pro unlocks unlimited vineyard profiles and full history.

Free
$0 / forever
Everything you need to get started.
  • GDD calculation for any location
  • Any vintage year
  • Winkler region classification
  • 1 saved vineyard profile
  • Current season live tracking
  • Full vintage history
  • 3-vintage comparison
  • Southern Hemisphere
Pro
$4.99 / month
$39.99/year — save 33%. For serious viticulture professionals.
  • Everything in Free
  • Unlimited vineyard profiles
  • Full vintage history per vineyard
  • 3-vintage comparison with accumulation chart
  • Southern Hemisphere support

Built in Napa Valley,
for the people who grow there.

Join viticulture professionals already tracking their growing season on Contra Calor.

🍎 Download on the App Store

App Store launch coming soon · iOS only