Edmonton, Alberta, Canada

Frost dates for Edmonton

The full distribution rather than a single date. Every figure below is a percentile of 30 years of daily minimum temperatures at this location, expressed as the date it fell on.

Median last spring frost

13 May

Half of years are later than this. Not a planting date.

Median first autumn frost

26 September

The far end of the outdoor season.

Frost-free season

137 days

Between those two dates in a median year.

Last and first frost by severity

Read a row as: in this fraction of years, the last frost of spring had already happened by this date. The 90% column is the cautious planting date; the 10% column is the gamble.

Light frost — nights at or below 0°C (32°F). Air temperature reaches freezing. Kills basil, beans and unhardened tomatoes; hardy crops shrug it off.
Frost	1 year in 10	Median	9 years in 10	Earliest	Latest
Last of spring	1 May	13 May	22 May	26 Apr	1 Jun
First of autumn	13 Sep	26 Sep	8 Oct	8 Sep	22 Oct
Frost-free days	160	137	114	every year on record saw this

Moderate frost — nights at or below -2.2°C (28°F). Damages half-hardy plants and most blossom. This is the threshold that decides a fruit crop.
Frost	1 year in 10	Median	9 years in 10	Earliest	Latest
Last of spring	18 Apr	2 May	13 May	16 Apr	22 May
First of autumn	17 Sep	4 Oct	15 Oct	11 Sep	24 Oct
Frost-free days	180	155	127	every year on record saw this

Hard frost — nights at or below -4.4°C (24.1°F). Ground freezes and even hardy crops check their growth. Effectively the end of the outdoor year.
Frost	1 year in 10	Median	9 years in 10	Earliest	Latest
Last of spring	7 Apr	17 Apr	5 May	27 Mar	13 May
First of autumn	30 Sep	15 Oct	2 Nov	14 Sep	7 Nov
Frost-free days	210	181	148	every year on record saw this

Dates in the southern hemisphere are computed on a growing year that starts in July, which is why "last of spring" falls where it should rather than in the middle of the calendar.

Chance of frost, week by week

Chance of at least one air frost during each week of the year, measured across the full record. The flat stretch in the middle is your frost-free season.

Temperature through the year

Mean monthly temperature across the record. Months shown in blue average at least one air frost.

Monthly means and average number of frost nights.
Month	Mean low	Mean high	Frost nights
January	-15.4°C	-7.2°C	30.4
February	-13.6°C	-4.3°C	28.2
March	-8.3°C	1.6°C	30.4
April	-1.9°C	9.8°C	21
May	4°C	16.3°C	4.8
June	8.8°C	20.1°C	0
July	11.7°C	23.1°C	0
August	10.5°C	22.6°C	0
September	5.7°C	17.7°C	2.6
October	-0.7°C	9.5°C	16.7
November	-7.6°C	-0.5°C	28.5
December	-13.8°C	-6.6°C	30.6

Turn these dates into a planting calendar →