I'm pleased to announce a new resource for you to use on Garden.org, the Frost Dates Lookup tool. Enter your zipcode and find out everything you wanted to know (and more) about when frosts and freezes occur in your area.

https://garden.org/apps/frost-...

I only have climate data for the US, so this unfortunately only works with our US members.

In addition to the direct link above, you can also find it under the Tools & Apps dropdown in the menu bar at the top of the page.

Very cool Dave - thank you

Beautiful photo too!

Yay, time to take the greenhouse down!

@dave, what climate data would you need to make it work for other countries?

And thankyou for your continued hard work to improve the site!

Not that I need it but what a great tool for those who do!

Great resource. Thanks

Am I the only one who is too stupid to understand the frost charts?

ShadyGreenThumb said:Am I the only one who is too stupid to understand the frost charts?

I hate charts and graphs! When I see them my first reaction is duh! I didn't do great in physics class. On the chart, find a date going across a 'last temp' (meaning probably the last time for that temp in a season) and then go up to the top of the column and read the percentage or likelihood that you could potentially see that temp on that date.

So - using zip 77435, which brings up Humble, TX, find Feb. 25 and there is a 20% chance to have a 28F temp on that date. Did this help - or is it still clear as mud?

It's why dealing with Texas weather, even in a friendly part of anywhere, is gambling. It's about probabilities, but when unlikely weather patterns string together for too long it can set plants, people and animals up for unpleasant experiences. The charts are probably better than zones if only because they are based on historical temperatures in a more specific location.

edited to add the date searched.

It appears that the NGA Frost Date calculator is using the 80% confidence level to estimate frost dates, since it says the Spring/Fall dates for my Zone 6 location are Apr 16/Oct 30 for a light frost and Mar 11/Dec 3 for a heavy freeze. These were somewhat surprising, but looking at the average (50%) columns for a 36° frost gives May 5/Oct 19, much closer to the last/first frost dates I had been using in my Zone 6 garden.

Out of curiosity I checked several other sites with frost predictions. It was sometimes difficult to tell whether they were using average (50% probability) or safe (i.e. “last” spring frost, “first” fall frost - 80-90%) dates but I’m using my best guess.
                                        Average Dates      Safe Date
Farmer’s Almanac       Apr 29/Oct 17
Dave’s Garden              Apr 30/Oct 10       May 18/Sep 28
Bonnie Plants              Apr16-30/Oct 16
Victory Seeds                                                May 8/Oct 2
Old Farmer’s Almanac Apr 19/Oct29
HowDo                                                            May 7/Nov 8
NOAA                              Apr 15-29
First Edition                                                    May 8/Oct 2

The national weather service records temperature data in stations several feet high so the ground temperature may be significantly different. I suppose that is why NGA is using the 24° figure for a “freeze” and the 36° figure for a “frost”. Which dates you decide to use depends on whether you are an optimist of pessimist, but I think I may end up in the “better safe than sorry” category.

The problem with the 'better safe than sorry' for folks that live in more arid areas that might have warm to hot temperatures is that waiting 'til the danger of frost is past, you've also waited past the time when the plants can manage the heat and dry conditions. It's always a crap shoot. Plant too soon and you might have to replant due to a freezing spell; plant too late and the plants simply don't flourish and there is no return for the effort. Watching the historical dates can improve the odds, but in any given year that may not work. Even natives and established plants get fooled by the weather. In this area, reliable peach crops are a doubtful proposition because the plants are tricked into bloom too early. Decades ago, it didn't happen as often. Not many around here attempt peach orchards anymore.

Donald @needrain to the rescue! It's the read up and down, read sideways charts that bother me. Unless its totally spelled out up,diwn and sideways, I'm never sure what I'm looking at.... then add those percentages! Always considered myself an intelligent person until faced with that kind of chart! That, and the theory of negative pressure.

Thanks very much, Dave!

Laying it out that way helps me see the period during which 4-5 degrees of extra frost protection might stretch my season by six weeks. And if I knew I could reliably maintain 10 degrees of overnight warmth ... twelve weeks? That's getting to be year-round growing.

It always puzzles me why people would go by a "50%" date. I'm not so ambitious as to WANT a 50% likelihood that everything I plant will freeze to death. I might gamble on a 30% probability of "killing them all" , IF I'm sure I'll have time to try again that season.