What Temperature Should a Greenhouse Be? Guide to Optimal Growth

Greenhouses are an invaluable tool for farmers, allowing you to extend growing seasons, protect crops from harsh weather, and grow a wider variety of plants. But greenhouse farming is only as successful as the environment inside it.

Temperature plays a crucial role in plant health and productivity. Too hot or too cold, and your plants could suffer from stress, stunted growth, or even death. Mastering greenhouse temperature control is the key to thriving crops. But you might be wondering, what temperature should a greenhouse be for optimal plant growth?

Read on to find out.

What Is the Ideal Temperature for a Greenhouse?

Every crop has its preferred conditions, but most greenhouse plants thrive within a daytime temperature range of 65-80°F and a nighttime range of 60-70°F. This balance ensures that plants can photosynthesize efficiently during the day while conserving energy at night.

Here’s why this range matters:

• Above 80°F: Plants may experience wilting, reduced flowering, and lower yields due to heat stress.
• Below 60°F: Growth slows down significantly, as the cooler temperature suppresses critical metabolic processes.

Focusing on maintaining this sweet spot will help ensure your crops perform at their best.

Seasonal Temperature Adjustments

Greenhouse temperature management isn’t a one-size-fits-all task. Adjustments need to be made depending on the season. Below, we explain how to optimize temperatures during winter and summer.

What Temperature Should a Greenhouse Be in Winter?

Winter can be challenging for greenhouse growers, as plunging outdoor temperatures make it harder to maintain the ideal internal climate. The question many growers ask is, what temperature should a greenhouse be in winter?

For most greenhouse crops, aim for the following ranges:

• Daytime: 65–75°F
• Nighttime: 55–65°F

To achieve this:

1. Use Heaters: Consider propane or electric heaters to keep the temperature consistent.
2. Insulate Your Greenhouse: Bubble wrap or thermal screens can help retain heat.
3. Monitor Lighting: Adding grow lights can generate additional warmth while promoting photosynthesis.

Proper heating during winter isn’t just about plant survival—it’s about maintaining their growth and health during the colder months.

What Temperature Should a Greenhouse Be in Summer?

The summer months can present the opposite challenge—excessive heat. It’s critical to prevent the internal temperature from soaring above 80°F. So, what temperature should a greenhouse be in summer?

Here’s your target:

• Daytime: 65–80°F
• Nighttime: 60–70°F

To keep temperatures under control:

1. Install Ventilation Systems: Open roof vents, side vents, or windows to allow hot air to escape.
2. Use Shade Cloths: Reduce direct sunlight exposure with 40–60% shade cloths.
3. Deploy Cooling Systems: Misting systems or evaporative coolers can help lower temperatures efficiently.

Taking steps to cool your greenhouse protects your plants from heat stress and ensures consistent growth, even at the peak of summer.

Guide to Nighttime Temperature

It’s tempting to think that nighttime temperatures are less important than those during the day, but this isn’t the case. Plants continue essential metabolic functions after the sun goes down, such as respiration and nutrient uptake.

You might now wonder, what temperature should a greenhouse be at night?

• Stick to 60–70°F at night for most crops.
• Too cold (below 55°F): Growth slows dramatically, and some plants may enter dormancy.
• Too warm (above 75°F): Plants burn through their stored energy, leaving them weakened.

Investing in a reliable thermometer or greenhouse thermostat can help keep nighttime temperatures within the ideal range. If temperatures dip too much, consider supplemental heating. Conversely, proper ventilation can lower the temperature if it remains too high.

Healthy nighttime temperatures not only help plants recover energy but also support robust root growth—a critical factor for pest and disease resistance.

Key Takeaways for Managing Greenhouse Temperature

Maintaining optimal greenhouse temperatures year-round isn’t just about plugging in heaters or opening vents—it requires careful monitoring and adjustment.

Your Greenhouse Temperature Checklist:

• Keep Daytime Temperatures: 65–80°F
• Maintain Nighttime Temperatures: 60–70°F
• Winter Tips: Use heaters, insulate with bubble wrap, and ensure adequate lighting.
• Summer Tips: Install ventilation, use shade cloths, and deploy misting systems.
• Invest in Tools: Use thermometers, thermostats, and humidity controllers to track and moderate conditions efficiently.

If there’s one takeaway, remember this: the better your temperature control, the higher your yield. Your crops will reward you with abundant, healthy growth for a job well done.

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