Climates seem to be forever changing, when we moved here over 40 years ago we could count on no frost after March 27, now it's more like late April.

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When I transferred dates from 2006 calendar to this years I came across my note - visible frost, May 2 & 3rd. Just a few miles from the moderating ocean here :)

Huh. My problem is that I often wind up working noon to nine, and my sleeping (and waking) schedule works accordingly. So I'm almost never up in time to see frost except in the dead of winter.

What I need is a maximum-minimum thermometer. And the determination to keep records [g].

It depends on what you are using this date for. If for setting out tender annuals that are sensitive to cold (coleus, basil, etc.) and hot weather crops (tomatoes, peppers), then Mother's Day is typically the guideline. In higher elevations or low-lying frost pockets, I'd even consider erring on the side of more towards the end of the month. Otherwise, many other annuals and cool season crops can tolerate light frosts pretty easily - perennials and everything else just don't care.

The Farmer's Almanac gives the Seattle/Tacoma average last frost date as 3/24 but that is really pushing it in my book.

If you were to consider the mildest local mesoclimates in our region and the coldest, and find the average dates of the last frost for each, you would indeed have a difference of more than a month... maybe two! Heck, some of the mildest places occasionally go through a winter with no frost at all. But as gardengal says, the last frost date has limited applications when it tends to be too cold and wet for many heat-loving vegetables and annuals before June (or May, depending on the plant).

As for exactly what your last frost date is - if you're on the valley floor it's probably sometime in May. If you're on a slope with good air drainage, it's probably earlier.

May 24th, is the rule of thumb most of us go by for tender stuff in my area. Any sooner you have to give some protection, if the soil hasn't started to warm up, the tender plants just sit and sulk and IMO sets them back.

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