What's with all these frost/freeze alerts?

What's with all these frost/freeze alerts?
Freeze Warning

By now you have probably heard meteorologists here in Columbus talk about things like, "A frost advisory is in effect and a freeze warning will be in effect starting tomorrow." You're also probably thinking a) Why all of a sudden am I seeing these alerts? And b) Why should I care about a freeze warning/frost advisory?

To start let's define these terms by looking at their definitions according to the NWS:

Frost Advisory: A widespread frost, which typically occurs with mainly clear skies and light winds, and low temperatures near or slightly above freezing(33-36 degrees)

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Freeze Warning: Low temperatures across the whole county/zone at or below 32 degrees.

Freeze Watch: Possibility that Freeze Warning Criteria may be met at longer rangers (24 to 48 hours out).

If you have been keeping track of our average high and low temperatures for the day, you would notice that our temperatures are gradually getting warmer (as expected) as we're now well into the spring transition.

Our average highs are now in the low 60's and our lows in the low 40's. Once we see our climatological averages get above the freezing mark, these alerts become issued when temperatures take a tumble back around freezing.

We've been seeing a lot more of these alerts due to the unseasonably cool air that's been stationed over central Ohio some of last week and now for much of this week.

In Columbus we typically see our average last 32 degree day in Spring on April 16 (this week). However, you'll see plenty of days past the 16 where temperatures will be flirting in the low 30's and that's okay.

Frost/freeze Climo for Ohio

You'll notice that not every location in Ohio will see it's last spring freeze on the same day, statistically speaking. That's because elements such as topography, urban or rural setting and placement of weather recording instruments can create a vast variety in temperatures across and area.

The NWS temperatures are officially taken at an elevation of five feet above ground, but the temperature at ground level may be colder.

On typical spring nights when frost occurs, the temperatures at the five foot level may read 36 degrees while at ground level it is actually the 32 degrees needed to form frost.

So why should you care? Well, many of us (farmers especially) pay very close attention to the weather when it comes time for outdoor planting. Certain hardy plants like lettuce and root vegetables can been planted once the ground thaws in March or April, but other plants can be very sensitive to these temperature drops and can be harmed or killed.

When we see frost advisories or freeze warnings, it's a good heads up for those to cover up their outdoor plants or bring them indoors if not planted yet.

6-10 day temperature outlook CPC

So when will we see our last freeze for spring? We've seen them as late as May 16..a month from Thursday. I don't think it'll be that late, but temperatures appear to stay in the low 30's at night through this weekend and then we'll see a slow warm up into average numbers early next week.

8 to 14 Day Temperature Outlook CPC

Beyond that, the CPC also has products for the 8-14 day outlook for both temperature and precipitation. It's showing slightly cooler than average conditions for the last week of April for much of the Great Lakes region, so I would bet that we continue to see these frost/freeze alerts stick around into May.