First and last freeze/frost dates for Denver, CO ,United States

First and last freeze/frost dates for:
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Each winter, on average, your risk of frost is from
October 1 through May 9.

Almost certainly, however, you will receive frost from October 14 through April 24.

You are almost guaranteed that you will not get frost from May 24 through September 18.

Your frost-free growing season is around 145 days.

Detailed station data* follows:

Lakewood, CO (Jefferson county):

Temperature10%20%30%40%50%60%70%80%90%
Spring 32° May 24 May 19 May 15 May 12 May 9 May 6 May 3 Apr 29 Apr 24
Spring 28° May 17 May 10 May 6 May 2 Apr 29 Apr 25 Apr 21 Apr 17 Apr 11
Spring 24° May 2 Apr 26 Apr 22 Apr 19 Apr 15 Apr 12 Apr 8 Apr 4 Mar 29
Fall 32° Sep 18 Sep 22 Sep 26 Sep 28 Oct 1 Oct 4 Oct 6 Oct 10 Oct 14
Fall 28° Sep 24 Sep 29 Oct 3 Oct 6 Oct 9 Oct 12 Oct 15 Oct 19 Oct 24
Fall 24° Sep 30 Oct 7 Oct 12 Oct 16 Oct 20 Oct 24 Oct 28 Nov 1 Nov 7

Boulder, CO (Boulder county):

Temperature10%20%30%40%50%60%70%80%90%
Spring 32° May 14 May 10 May 8 May 6 May 4 May 2 Apr 30 Apr 27 Apr 24
Spring 28° May 7 May 2 Apr 28 Apr 25 Apr 22 Apr 20 Apr 17 Apr 13 Apr 8
Spring 24° Apr 26 Apr 21 Apr 17 Apr 13 Apr 10 Apr 7 Apr 3 Mar 30 Mar 25
Fall 32° Sep 18 Sep 23 Sep 26 Sep 29 Oct 2 Oct 5 Oct 8 Oct 11 Oct 16
Fall 28° Sep 23 Sep 29 Oct 4 Oct 8 Oct 11 Oct 15 Oct 19 Oct 23 Oct 30
Fall 24° Oct 3 Oct 10 Oct 15 Oct 20 Oct 24 Oct 28 Nov 1 Nov 6 Nov 13

Evergreen, CO (Jefferson county):

Temperature10%20%30%40%50%60%70%80%90%
Spring 32° Jun 18 Jun 13 Jun 9 Jun 6 Jun 3 May 31 May 28 May 24 May 18
Spring 28° Jun 2 May 28 May 24 May 21 May 18 May 15 May 11 May 7 May 2
Spring 24° May 18 May 13 May 9 May 6 May 3 Apr 30 Apr 27 Apr 24 Apr 19
Fall 32° Sep 4 Sep 8 Sep 11 Sep 14 Sep 16 Sep 19 Sep 21 Sep 24 Sep 28
Fall 28° Sep 12 Sep 17 Sep 21 Sep 24 Sep 27 Sep 30 Oct 3 Oct 6 Oct 11
Fall 24° Sep 20 Sep 25 Sep 28 Oct 1 Oct 4 Oct 6 Oct 9 Oct 12 Oct 17

* This station data is available courtesy the National Climatic Data Center.

For each weather station, you will see a temperature along with tables of data organized into percentage columns. The percentage column tells you the probability that you will experience that row's temperature on or near that date. Here are two examples to help you determine your probable last frost and first freeze dates.

Example 1 (Last Frost). In the Spring 32° row, if you have "Apr 15" under the 50% column, that means you have a 50% chance of seeing frost on or before April 15th.

Example 2 (First Freeze). In the Fall 24° row, if you have "Dec 1" under the 90% column, that means you have a 90% chance of seeing 24 degrees on or after December 1st.

Empty cells indicate you have a less than 10% chance of ever seeing that temperature.

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