Hi Jill, thanks for using Ask Extension.

The sudden wilting appears to be driven by heat and water not fully reaching the deeper roots. Genesee County is seeing high heat this week, and cucumbers in a tall tunnel can wilt quickly under those conditions, even when the soil looks damp on top. Adding about 30% shade cloth over the tunnel during the hottest part of the day and keeping an eye on temperatures can help reduce heat stress. Improving air circulation — even a small fan to move air through the tunnel — can also help reduce heat and humidity around the plants. Checking soil moisture by digging down a few inches will show whether water is getting deep enough; with adequate irrigation, the plants should begin to recover. Try to avoid overwatering, as the soil should be moist but not soggy. Treating the powdery mildew will also reduce extra stress. After a heat‑related wilt, cucumbers often need some time to bounce back. If you can share how you’re watering (how often, how long, and what system you’re using) we can help confirm whether the plants are getting enough water.

Check out the following link:

Keep gardens thriving through the heat | UMN Extension

I hope this is helpful.

On Mon, Jul 13, 2026 at 7:20 PM, Ask Extension

wrote:

Hi Jill, 

Thanks for the additional details. With overhead sprinklers running twice a day for 7 minutes, the main thing to check is whether that water is actually reaching the deeper root zone. Overhead systems often wet the leaves and the top surface more than the soil below, especially in a tall tunnel, so the plants can still wilt even when the surface looks damp. Digging down a few inches after a watering cycle will show whether moisture is getting deep enough. Hand‑watering during the heat can help, but when temperatures climb above 90°F the plants may still wilt because they can’t move water fast enough. Reducing heat in the tunnel and treating the powdery mildew will also help lower stress.