Weather Data in Vineyard Spray Records: What You Must Capture and Why

By VitiScribe Editorial·June 29, 2025·Updated September 1, 2025

Weather data is missing from 28% of California vineyard spray records reviewed in DPR audits. That's more than one in four records that are incomplete on a required field, not a discretionary one.

California DPR requires weather conditions at the time of application on every pesticide use record. Temperature, wind speed, and wind direction are the minimum. Most state regulators have similar requirements. This isn't a formality. Weather conditions at application time are relevant to drift risk assessment, application timing compliance, and label requirement verification.

When an auditor reviews your records and the weather fields are blank or estimated, that's a required field violation.

TL;DR

Weather data is missing from 28% of California vineyard spray records in DPR audits -- temperature, wind speed, and wind direction are required fields, not optional ones; blank or estimated weather data creates citable violations
Estimates don't hold up in audits: "felt calm" is not a documented wind speed measurement; defensible weather data comes from an on-site station, nearest CIMIS station with a timestamped reading, or a calibrated handheld anemometer documented at application time
Many pesticide labels include wind speed maximums (commonly 10-15 mph) -- weather records that show application above the labeled maximum are documented label violations, which are violations of FIFRA
CIMIS (California Irrigation Management Information System) operates 145+ weather stations throughout California's agricultural regions and archives historical hourly data; for past applications with blank weather fields, CIMIS can be used to reconstruct documented readings with notation of the data source
Weather context documents IPM rationale: "Applied at 78°F with moderate humidity following three days of overcast conditions" is an IPM record; "Applied June 15" with blank weather fields is a calendar spray record with missing required fields
VitiScribe auto-populates weather fields from your connected station or nearest CIMIS/AgWeatherNet station at the time of logging, documenting the data source in the record for audit traceability

What Weather Data Is Required

California DPR Requirements

California DPR's required application record fields include:

Temperature at application time
Wind speed
Wind direction

These are the baseline. Some products have label restrictions that add requirements: "Do not apply when wind speed exceeds 10 mph" creates a compliance attestation embedded in the weather data. If your record shows a 14 mph wind speed on a product with a 10 mph wind restriction, you've documented a label violation.

Why Estimates Don't Hold Up

The problem with estimated weather data: estimates are not the same as measurements. If an auditor asks how you determined that wind speed was "approximately 5 mph" and your answer is "it felt calm," that's not a documented weather measurement.

Weather data that holds up in an audit comes from:

An on-site weather station that recorded conditions at application time
The nearest CIMIS station (California Irrigation Management Information System) with a timestamped reading for the application date and time
A calibrated handheld anemometer and thermometer reading documented at application time

"Looked outside" doesn't qualify. "Used the weather app on my phone" is better than nothing but still lacks the precision that a calibrated measurement provides.

Why Weather Records Matter Beyond Compliance

Drift Risk Documentation

Pesticide drift is one of the higher-consequence compliance issues in California viticulture. When drift complaints are investigated, the first question is what conditions were present at the time of application. Your weather records either support or contradict any account you provide.

If you applied on a morning when conditions were favorable, your records document that. If conditions changed mid-application and you had to stop, that should be in your records too.

Label Restriction Compliance

Many pesticide labels have specific application condition restrictions:

Wind speed maximums (commonly 10-15 mph)
Temperature maximums and minimums
Relative humidity minimums for some products
Time-of-day restrictions for bee-sensitive applications or for temperature-related efficacy

When your weather records consistently show conditions within label restrictions, you're building evidence that your application program respects those restrictions. When weather records are missing, you have no evidence either way.

IPM Decision Documentation

Weather conditions drive disease and pest pressure. When you document weather conditions at application time alongside your pest scouting observations, you're creating context for your spray decisions that makes them defensible as threshold-based IPM.

"Applied on June 15 when temperatures were 78°F with moderate humidity following three days of overcast conditions. Powdery mildew scouting on June 12 showed 4% infected shoots. Bloom stage." That's an IPM record. The weather context explains why the application was made at that time.

"Applied on June 15" with weather fields blank is a calendar spray record with missing required fields.

Vineyard spray program design covers how weather-based spray decisions integrate into a full-season IPM program that documents evidence-based management from scouting through application.

Sources for Weather Data in Vineyard Records

On-Site Weather Stations

The most defensible weather data comes from a calibrated weather station on your property recording conditions in real time. Stations from companies like Davis Instruments, Onset (HOBO), and Pessl Instruments record temperature, humidity, wind speed, and wind direction at user-defined intervals, typically every 5-15 minutes.

When your spray record shows weather data from your station at 8:47 AM on June 15th, that's documented measurement at application time. No estimation involved.

CIMIS (California)

The California Irrigation Management Information System operates over 145 weather stations throughout California's agricultural regions. CIMIS data is publicly accessible and provides hourly temperature, wind speed, wind direction, relative humidity, and other parameters for stations throughout major vineyard regions.

When you log a spray record, pulling the CIMIS reading from the nearest station for the application date and time gives you a documented weather source even without your own on-site station. The CIMIS station number and timestamp should be included in your record to document the data source.

CIMIS is most useful when the nearest station is within a few miles. Microclimatic differences in temperature and wind can be substantial between a CIMIS station and a vineyard block 5 miles away in a different topographic setting. On-site measurement is more accurate; CIMIS is an acceptable documented alternative.

AgWeatherNet (Washington)

Washington State University's AgWeatherNet system operates weather stations throughout Washington's wine-producing regions, including the Columbia Valley and Walla Walla. For Washington vineyard operators, AgWeatherNet provides the same function as CIMIS in California.

How VitiScribe Handles Weather Data

VitiScribe integrates with connected weather stations and pulls conditions automatically when you log a spray event. For operations with a connected CIMIS or AgWeatherNet account, the weather data at logging time populates automatically without manual entry.

For operations without connected stations, VitiScribe includes a CIMIS station selector where you identify your nearest station. When you log a record, the platform retrieves the most recent CIMIS reading for your selected station and pre-populates the weather fields. You confirm the data is representative of your application conditions.

The spray window alerts feature in VitiScribe uses weather data from your connected station to alert you when conditions cross into favorable spray windows or when wind conditions exceed label restriction thresholds.

VitiScribe's pesticide application records system stores weather data as a documented, timestamped field on every record rather than a manually-estimated entry.

What to Do When You Didn't Record Weather

If you're reviewing your records and finding weather fields that are blank or estimated, there are options:

CIMIS historical data: For California applications within the past few years, CIMIS archives are accessible online. You can retrieve the hourly data for the nearest station on the application date and retroactively document the weather conditions with a notation that the data came from the nearest CIMIS station at the logged application time.

This approach is better than a blank field, though an auditor may note that the data is reconstructed rather than contemporary. Consistent retroactive documentation across multiple records may itself raise questions.

Going forward is the priority: If your historical records have weather gaps, the most important thing is ensuring your current and future records have accurate, source-documented weather data. Retrospective reconstruction has limits.

Frequently Asked Questions

What weather data is required on a California vineyard spray record?

California DPR requires temperature, wind speed, and wind direction at the time of pesticide application as mandatory fields on every commercial pesticide use record. Additional weather parameters may be required by specific pesticide labels for products with application condition restrictions. Relative humidity is not a DPR-required field but is relevant for some label compliance situations and for disease risk documentation.

How does VitiScribe capture weather conditions at the time of spraying?

VitiScribe integrates with connected on-site weather stations to pull real-time conditions automatically when you log a spray event. For operations without connected stations, VitiScribe retrieves weather data from the nearest CIMIS station (California) or AgWeatherNet station (Washington) at the time of record creation and pre-populates the weather fields. Weather source is documented in the record for audit traceability.

What weather source does VitiScribe use if I do not have an on-site weather station?

For California operations, VitiScribe uses the nearest CIMIS station you've selected for your vineyard location. For Washington operations, AgWeatherNet provides the equivalent function. In both cases, VitiScribe retrieves the most recent hourly reading from the selected station at the time you log the record and pre-populates temperature, wind speed, and wind direction. The CIMIS or AgWeatherNet station ID is recorded with the weather data for audit documentation.

How should I retroactively document weather data for past spray records with blank weather fields?

For California applications, retrieve CIMIS historical hourly data for the nearest station for the application date and time. Enter the temperature, wind speed, and wind direction values and add a note in the record identifying the CIMIS station number, station name, and the specific timestamp of the reading. Example notation: "Weather data from CIMIS Station #047 (Napa Valley), reading at 08:00 AM on 06/15/2025." This documented reconstruction is substantially better than a blank field. Be consistent in your notation method across all retroactively updated records. If an auditor questions the retroactive documentation, the consistent source notation demonstrates good-faith reconstruction from a legitimate data archive rather than fabrication.

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Managing Contract Spray Applicators with Digital Records in Your Vineyard

Sources

California Department of Pesticide Regulation (CDPR)
California Irrigation Management Information System (CIMIS)
Washington State University AgWeatherNet
USDA Environmental Protection Agency (EPA) -- FIFRA label requirements
National Weather Service -- Agricultural Weather Products

Get Started with VitiScribe

Weather data is missing from 28% of California spray records in DPR audits -- a required-field violation that's entirely preventable with automatic weather capture. VitiScribe pulls temperature, wind speed, and wind direction from your connected station or nearest CIMIS/AgWeatherNet station when you log each application, documents the data source in the record, and alerts you when wind conditions approach label restriction thresholds. Try VitiScribe free and eliminate weather field violations from your records today.