News: From the Sidelines: The Science of the "Rain Out"

Date Published	Author
4/17/2026 12:00:00 AM	Portland Athletic Facilities Team

Picture it: Spring has finally arrived in Portland. The temps creep into the 60s, and those overnight lows of 25 are becoming a distant memory. The ground has thawed, and our baseball, softball, and multipurpose fields are finally open. But as every Mainer knows, April brings rain—sometimes a lot of it. While we rely on that rain for our gardens, we have to be mindful that using a field at the wrong time can cause damage that lasts for years.

The "Lung" of the Field: Sponges vs. Bricks.

In healthy athletic turf, the ground isn't solid. It’s actually about 50% solid matter and 50% "pore space" (air pockets).

Think of these spaces as the grass’s lungs. Large gaps (macropores) act as vents to allow water to drain and oxygen to reach the roots. Smaller gaps hold just enough moisture to keep the grass hydrated during a dry spell. When soil is dry, the particles lock together, protecting these "air bubbles" from popping when you walk on them.

However, when the soil is saturated, water acts as a lubricant. The structure softens, and the weight of an athlete "pops" the bubbles, crushing the soil into those air pockets. When the field eventually dries, it re-hardens without those lungs—turning from a resilient sponge into a concrete brick. This makes it nearly impossible for roots to breathe or for future rain to drain, leading to a "puddle effect" that lasts all season.

The "Spring Thaw" Complication 

In Portland, the ground is often still frozen or cold a few inches down in April. Rain has nowhere to go but to sit in that top layer of "mush." This is the primary reason we often wait until May to fully schedule our grass fields: we wait for the "deep thaw" so the sponge can actually drain.
"But the dirt looks okay?" 

You might be tempted to stay off the grass and just play on the diamond. But saturated infields are fragile. Like handprints in wet concrete, the ruts and impressions in mud will harden into "lips" and uneven ruts. This doesn't just make the next game difficult; it makes it a safety hazard.
Furthermore, playing on wet dirt "churns" the surface, mixing our expensive top-dressing with the sub-base layer and ruining the drainage system our crews worked all spring to prepare.

The 2:00 PM Decision. 
We know it’s frustrating when the rain stops at 10:00 AM, but the field is still closed at 4:00 PM. We use the sun as our most powerful drying tool. We wait until 2:00 PM on weekdays to make closure decisions, giving the sun every possible chance to make the fields playable.
Manually drying a field is labor-intensive. It requires "Turfus" (a drying agent) and many man-hours to spread, drag, and level the surface. With 12 diamonds and a limited crew, we must prioritize games over practices to ensure the greatest public benefit.

When to Call it: The "Shear" Factor 

If it starts raining during your rental, look for the "Shear Factor." From a science perspective, wet grass loses its "shear strength." If cleats are slicing through the root zone like a knife through butter instead of gripping the dirt, the field is being damaged. At that point, the safest—and most responsible—choice for the season is to head to the sidelines.

While we all want to hear the whistle blow and the “play ball” call as soon as possible, our priority is ensuring that when you do take the field, it is safe and built to last. By respecting “Rain Out” closures, you are helping us prevent permanent compaction and ensuring our fields stay like sponges, not bricks.