Peas aren't grass, and production in peas slows down significantly in warm weather. They may do very well as young plants, but you will likely have a much shorter harvest if summer temps come early to your garden this year. That will negate any advantage gained by starting in pots. I think you would be better served by putting them out when night-time lows are in the mid 30s and the days are simply warmer than that. It is not ambient air temperature that pea growth responds to, but soil temps. Air temps are primarily important in terms of the danger of frost, and have less effect on growth and production.

Seconding what Bill said.

The golf course greenskeeper's formula may work very well on certain grass species. It wouldn't work at all on a different grass species. For example Kentucky bluegrass and bermuda grass have very different cultural requirements, and there exist both cool-season and warm-season grasses.

Peas aren't grasses at all, and are very different from grasses. A version of the greenskeeper's formula may work, but the formula for peas might be overnight low + daytime high = 80 instead of 100, for example.

Peas are cool-season crops, and suffer when the warm weather sets in. They need to be started well in advance of when grasses get going.

Interesting Stuff...thanks for the responses

Here is what I am facing (in Western Oregon)
Yesterday... LOW 29 HIGH 45

OK, to me neither the soil temp or the air temp would be conducive to plant growth...even a cool weather crop, such as peas. Under these conditions, it was not raining but the sun didn't appear until late afternoon so things never warmed up. I have been gardening for (only) six years so my experience is limited, but my observation is that peas planted at this time do not germinate well...therefore I went to starting them in cell trays. They are my unheated greenhouse now and are growing some there. I would say yesterday's range in there was (like) 34 to 65. I don't want to go to "analysis paralysis" ...but there might be a useful quantitative number that I might use...any other thoughts welcomed

I am in eastern Washington and we usually plant peas in March or early April. The high is probably 45 to 50 and the low 30. If we waited for the combined 100 degrees...it would probably be June :)

Cool soil temps slow down pea germination, but they will continue to grow once seed dormancy is broken. Were I in your position, I would install plastic row covers over the bed where the peas are to be transplanted, give the soil a few days to warm, then set out the peas under fabric row covers until most or all frost danger is passed. Then remove the covers to encourage cooler growing temps till it sets a crop. That way you get the longest possible harvest period before summer heat shuts them down.

Yesterday... LOW 29 HIGH 45

OK, to me neither the soil temp or the air temp would be conducive to plant growth..

So what is your soil temp? You don't mention it and that is what will determine when to plant them out. Measure the soil temp and no "analysis paralysis" will be needed. :)

I can plant peas in late Feb. because the bed I use for them is raised so it warms faster and it has been covered with black landscape fabric since the first of the month. By the time I plant next week the soil will easily be 60 degrees.

Dave

Owing to the absence of sunshine, I am afraid that the soil temp does not reach the ambient high...but I do have some clear plastic with which I will cover my raised bed.

There is a saying that is only a slight exaggeration...
THE OREGON PEOPLE DON'T TAN...THEY RUST!

In western WA (over 50 miles from Puget Sound)...

I've presprouted peas inside & planted them outside when the soil temp at 1" depth is a at least 40 degrees. I use my digital food thermometer inside a baggie.

When I've planted the next group 2 weeks later it catches up with the 1st group, so that by harvest there's no difference between the 2 plantings.

...if you have raised beds, containers, a hoop house or row cover that 40 degree soil will happen sooner...

but I do have some clear plastic with which I will cover my raised bed.

Clear doesn't give the same soil heating effects as black plastic does.

Dave

I think corrine1 has brought up a point that I have noticed in my (limited) experience here in the PNW.

When I've planted the next group 2 weeks later it catches up with the 1st group, so that by harvest there's no difference between the 2 plantings.

The first plantings of peas kind of sit there until the sun reappears and warms things up a bit. This is why I was looking for a temperature guideline

It seems like if you warm up the soil with black plastic, the effect will be marginal, if after you remove it, the overnight low dips below freezing and the sun doesn't appear to warm it back up during the day.

This affect is what keeps Californians down there and why coffee was invented in Seattle

You have only to warm the soil for germination. After that the sprouts will grow just fine in cool soil.