Greenhouse Weather Management

What does weather do to a greenhouse?

Sun heats the space quickly, and a clear day can push temperatures far above the outside air. Cold nights lose heat fast through glazing. Humidity builds when air is trapped, which invites disease. Wind and snow add stress to the structure.

Managing these swings is the core of greenhouse growing.

Keep the covering clean. Dust, algae and film reduce light, and old plastic or glazing may become brittle and fail in wind. Inspect and replace on a schedule suited to your material.

How do I manage heat?

Ventilation is the first tool. Open vents, doors and sidewalls so hot air escapes and cooler air enters. Shade cloth reduces light and heat on bright days. Fans can help move air.

Watch for heat stress in plants: wilting, scorched leaves and blossom drop. Because crops differ in their limits, check your crop's guidelines with Extension rather than guessing.

Watering needs change with weather. Plants dry faster on bright, breezy days and slower on cloudy ones. Check the media instead of following a fixed schedule, and avoid watering late in the day in cool weather.

• Vents, doors and sidewalls
• Shade cloth
• Fans for air movement
• Watering at the right time

How do I manage cold?

Keep a thermometer that records minimum and maximum temperatures and check it each day. On cold nights, consider thermal covers, double layers and sealed gaps. Water in containers can store a little heat, though not enough for severe cold.

Heaters in greenhouses must be installed and vented properly, since fuel-burning units can produce carbon monoxide and carry fire risk. Have a qualified professional install and inspect them, and install a carbon monoxide alarm where appropriate.

Seedlings are the most sensitive. A few hours of extreme heat or cold can wipe out a tray, so check them first during any weather swing and have a protection plan, such as moving trays to a safer spot.

• Keep a min-max thermometer at plant height
• Seal gaps and add a second layer on cold nights
• Have heaters installed and inspected by a professional
• Use a carbon monoxide alarm where fuel is burned

How do I control humidity and disease?

Good airflow and moderate watering reduce humidity-driven diseases. Water early in the day so leaves dry, and avoid overcrowding. Space plants so air moves between them.

Scout often. If you see spots, mold or pests, ask your Extension agent to identify the issue before treating anything, and always follow label directions for any product.

Learn the signs of too much or too little light, from stretched seedlings to bleached leaves. Adjust shading and spacing, and record what you change so you can repeat what worked next season.

• Water early in the day
• Space plants so air can move
• Remove diseased leaves promptly
• Ask Extension to identify problems

What about wind, snow and structural safety?

Anchor the structure well. Check the covering for tears, tighten fasteners and clear snow load promptly if your design requires it. Do not enter a greenhouse that looks overloaded or sagging.

Local building and zoning rules may apply to greenhouses. Ask your county planning office, and ask Extension about designs that suit your snow and wind conditions.

How can I monitor and automate?

Thermometers, hygrometers, and controllers for vents and fans can lower labor and risk. Automation is helpful, but it can fail, so check it regularly and have a backup plan for power loss.

Keep a daily log of highs, lows, watering and any problems. Over time, you will learn how your greenhouse behaves in each season.

How do I plan for power loss and breakdowns?

Fans, heaters, controllers and watering systems may all depend on electricity. Decide in advance what you would do if power fails on a freezing night or a sunny, hot afternoon. A manual way to open vents, a backup heat plan and a reliable way to be alerted are worth having.

Alarms that call or text you when the temperature moves outside a set range can save a crop. They only help if you can reach the greenhouse safely and in time.

Do not run generators indoors or in enclosed spaces, and never bring fuel-burning equipment into a greenhouse unless it is designed for that use and installed properly. A licensed electrician or qualified technician should handle any wiring.

• Manual vent opening
• Backup heat plan
• Temperature alarms
• Safe generator use outdoors only

Last reviewed: November 12, 2026. Written by the Rural Farm Life Editorial Team. See our editorial policy.