(Originally published on ONgreenhousevegetables.ca on June 14, 2026 by Greenhouse Floriculture Summer Student Kendra van der Wier )
Welcome to the Vineland DLI report for June 2026! Here in Vineland, June has been a sunny and very hot month!
In June 2026, Vineland received 53% more light in June than in April! (May 2026 data was not available).
Read on for detailed graphs and more information.
Only looking for certain information? Use the table of contents to navigate between sections:
Data Summary – Leamington & Vineland
DLI data were available for two and half weeks in June for Leamington-Kingsville. The average DLI for the month of June 2026 for Leamington-Kingsville was 61 moles/m2/day. The maximum DLI was 73.1 recorded on June 7th, and the minimum DLI was 38.9 recorded on June 21st.
DLI data were available for two weeks in June for Vineland. The average DLI for the month of June for Vineland was 49 moles/m2/day. The maximum DLI was 75.1 recorded on June 6th, and the minimum DLI was 22.8 recorded on June 25th.
Leamington-Kingsville received 22% more light in June than May. The monthly DLI average for June 2026 is 15% high than it was in June 2025. Last month’s data were not available for Vineland but compared to April it received 53% more light in June. Vineland received 20% less light than Leamington-Kingsville.
Monthly Radio Report
Tune in on the second Tuesday of each month at 12:00 pm during the Noon Farm Show on CFCO Country 92.9, covering Windsor to Woodstock. Not in the area? You can listen live online at country929.com.
Background
We mounted a daily light integral (DLI) meter on the border of Leamington and Kingsville, Ontario, in 2024, and another DLI meter at the Vineland Research and Innovation Centre (VRIC) in Vineland, Ontario, in 2025 to give greenhouse producers in those areas access to readily available light data.
If you are interested in the full Vineland data, you can download the excel sheet at the bottom of this post.
Daily light integral (DLI) and photosynthetic photon flux density (PPFD) data are important to greenhouse production because they measure the amount of light that is available to the crop. This data can be used to adjust the growing environment, such as irrigation and carbon dioxide levels, to optimize photosynthesis and crop yield.
DLI is the total amount of light within the photosynthetically active radiation (PAR) spectrum (light wavelengths of 400-700 nm) that impacts a surface in a day. It is measured in moles per metre squared per day (mol/m2/day).
PPFD is the total amount of light within the PAR spectrum that impacts a surface every second. It is measured in micromoles per metre squared per second (µmol/m2/second).
The data provided here reflects the amount of outdoor light. The amount of light that greenhouse crops receive inside a greenhouse can be significantly lower (90-50%) and is affected by the cover material (clear glass, diffused glass, single polyethylene, double polyethylene, triple polyethylene, etc.), cover material treatment (whitewash), and curtains (shade, energy, blackout, etc.). The ideal DLI inside a greenhouse is different for each crop. You can find more information on DLI levels for greenhouse fruit and vegetable crops in the production guides available in the OMAFA Greenhouse Fruit and Vegetable Publications section of the ONgreenhousevegetables.ca blog.
Objectives
The DLI and PPFD Data section of this blog provides greenhouse producers in southwestern Ontario and Niagara Region with outdoor light levels on a regular basis year-round. It is meant to serve as a record of the amount of light these locations received on a daily basis throughout the year.
Each blog post in this section contains tables with the available data for a one-month period and an Excel file with data from previous months.
NOTE: This data is provided for information purposes and does not represent the amount of light at other locations.
Materials and Methods
The data was collected using DLI-600 sensors from Apogee Instruments. They measured the extended PAR (ePAR) spectrum (400-760 nm), which includes far red light. The sensors were placed 90 cm off the ground outside of a greenhouse at the Leamington-Kingsville border and at VRIC in Vineland, Ontario.
When possible, a NanoLambda light meter was also used to measure irradiance (W/m2 for light in the 340-1010 nm spectrum range) and PPFD (µmol/m2/second for light in the 400-700 nm spectrum range) at a specific date and time. It was placed beside the Apogee light meter when measurements were taken.
Available DLI data is presented for each month in Figure 1 and Table 1, for each week in Figure 2 and for each day (24 hr period) of the current month in Figure 3 and Table 2. It is all available to download in the attached Excel sheet in the last section.
DLI Data
Figure 1: Available monthly DLI data for Leamington-Kingsville and Vineland in 2024, 2025 and 2026 presented in two graphs. A) Bar graph representing average ± standard deviation, and B) box whisker graph representing the average (indicated by the x within the box), median (indicated by the horizontal dash within the box), 25-75% of the data (indicated by the box) and minimum and maximum values (indicated by the ends of the whiskers or outlier values above and below the box).
A)
B)
Table 1: 2025 and 2026 monthly DLI data for Leamington-Kingsville and Vineland. NA = not available.
Figure 2: Available weekly DLI data for Leamington-Kingsville and Vineland in 2024, 2025, and 2026. Week 1 = January 1-7, week 2 = January 8-14,…,week 52 = December 24-31.
Figure 3: June 2026, daily (24 hr period) DLI data for Vineland.
Table 2: June 2026, daily (24 hr period) DLI data for Leamington-Kingsville.
DLI and PPFD data Excel Sheet