USDA Hardiness Zone 6b
Frost Dates for 63367 — Lake St Louis, Missouri
NOAA 1991–2020 normals from Weldon Spring NWS, MO (610 ft), 9 miles southeast.
Updated
In Lake St Louis, the last spring frost (32°F) is around April 10 in half of years and has passed by April 26 in nine years out of ten. The first fall frost comes around October 26, as early as October 12 one year in ten, leaving a typical freeze-free season of 199 days (NOAA, Weldon Spring NWS, MO).
- Last spring frost
- April 10
- First fall frost
- October 26
- Growing season
- 199 days
- Hardiness zone
- 6b
50% probability
50% probability
freeze-free, 50%
-5 to 0°F (-20.6 to -17.8°C) coldest night
- First snow
- December 5
- Last snow
- March 8
- Winters with snow
- 96%
- Snow per year
- 13.5"
median, 1991–2020
median, 1991–2020
24 of 25 observed
NOAA normal
Frost risk by date in Lake St Louis
Half of springs at Weldon Spring NWS, MO see their last 32°F night by April 10; only one in ten is past it by March 26, and one in ten still has one after April 26. Planting tender crops after April 16 leaves a 30% risk of a frost on them, after April 20 20%, and after April 26 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 35% of the 158 Missouri stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 26 in half of years, as early as October 12 one year in ten, and holds off past November 8 one year in ten. A hard freeze of 28°F follows 10 days later, around November 5; in spring the one-in-ten date for 28°F is April 15, 11 days before the 32°F one. The freeze-free season lasts 199 days in a typical year, longer than at 64% of the 158 Missouri stations; it reaches 220 days one year in ten and falls short of 178 one year in ten. On average 105 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 12 days longer, to about April 22, and return around October 16. Severe cold of 16°F or below comes every winter, usually between December 9 and March 2.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 8 | Apr 12 | Apr 15 | Apr 19 | Apr 22 | Apr 25 | Apr 29 | May 2 | May 6 |
| 32°F | Mar 26 | Mar 31 | Apr 4 | Apr 7 | Apr 10 | Apr 13 | Apr 16 | Apr 20 | Apr 26 |
| 28°F | Mar 12 | Mar 19 | Mar 23 | Mar 27 | Mar 31 | Apr 1 | Apr 4 | Apr 8 | Apr 15 |
| 24°F | Mar 2 | Mar 7 | Mar 12 | Mar 15 | Mar 19 | Mar 22 | Mar 26 | Mar 30 | Apr 3 |
| 20°F | Feb 20 | Feb 28 | Mar 3 | Mar 6 | Mar 9 | Mar 12 | Mar 16 | Mar 19 | Mar 25 |
| 16°F | Feb 9 | Feb 17 | Feb 23 | Feb 28 | Mar 2 | Mar 5 | Mar 9 | Mar 13 | Mar 18 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 1 | Oct 6 | Oct 10 | Oct 13 | Oct 16 | Oct 18 | Oct 21 | Oct 24 | Oct 28 |
| 32°F | Oct 12 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Oct 31 | Nov 2 | Nov 8 |
| 28°F | Oct 22 | Oct 28 | Oct 31 | Nov 2 | Nov 5 | Nov 8 | Nov 12 | Nov 16 | Nov 22 |
| 24°F | Nov 2 | Nov 6 | Nov 10 | Nov 13 | Nov 17 | Nov 21 | Nov 25 | Nov 29 | Dec 3 |
| 20°F | Nov 9 | Nov 15 | Nov 19 | Nov 24 | Nov 28 | Dec 1 | Dec 5 | Dec 9 | Dec 16 |
| 16°F | Nov 17 | Nov 25 | Nov 30 | Dec 4 | Dec 9 | Dec 13 | Dec 18 | Dec 23 | Dec 28 |
Freeze probabilities 1991–2020 at Weldon Spring NWS, MO, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 63367 →Compare Lake St Louis with another place →
Weather by month in Lake St Louis
July is the warmest month at Weldon Spring NWS, MO, averaging 88°F by day and 67°F at night; January is the coldest at 39°F and 21°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 79% of years.
Warmth for growing adds up to 4,025 growing degree days a year (base 50°F), fewer than at 53% of the 158 Missouri stations. 37% of them (1,479) have built up by the end of June, and July adds the most, 849. Precipitation totals 44.4 inches a year, most in May (5.1") and least in February (2.4"); May to September bring 47% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 39 | 21 | 2.6 | 100% | 26 | 5 |
| Feb | 45 | 24 | 2.4 | 100% | 22 | 14 |
| Mar | 55 | 33 | 3.7 | 100% | 15 | 70 |
| Apr | 67 | 44 | 4.7 | 79% | 4 | 219 |
| May | 76 | 54 | 5.1 | 5% | 0 | 466 |
| Jun | 84 | 63 | 4.7 | 0% | 0 | 705 |
| Jul | 88 | 67 | 3.9 | 0% | 0 | 849 |
| Aug | 87 | 65 | 3.6 | 0% | 0 | 807 |
| Sep | 80 | 57 | 3.5 | 1% | <1 | 553 |
| Oct | 68 | 46 | 3.4 | 71% | 2 | 254 |
| Nov | 55 | 35 | 3.7 | 100% | 13 | 71 |
| Dec | 44 | 26 | 3.1 | 100% | 23 | 11 |
Monthly normals 1991–2020 at Weldon Spring NWS, MO (610 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, St Peters 2 SE, MO, 11 miles east of Lake St Louis, has a last frost 1 day earlier (April 9), the same first-frost date, a season 1 day shorter.
When it snows in Lake St Louis, Missouri
The first measurable snow (0.1 inch or more) in Lake St Louis usually arrives around December 5, and the last of the season around March 8. Those are the middle dates across the winters of 1991–2020 at Weldon Spring NWS, MO, 8.7 miles away: half of years saw snow earlier, half later. Snow fell in 96% of those winters. The last 32°F night of spring typically comes 33 days after the last snow.
Planting calendar for 63367
| When | What to do |
|---|---|
| January 30 – February 13 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 13 – February 27 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 13 – March 27 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 10 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 3 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 12 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 26 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 63367 is 9 miles from Weldon Spring NWS, MO, which stands at 610 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 63366 (O Fallon). The 2023 USDA Plant Hardiness Zone Map lists ZIP 63367 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.