Last frost date in Monrovia, CA

Average last frost
April 28

In Monrovia, the last spring frost comes around April 28 in an average year. Wait until May 27 if you want 90% odds of no more frost. The first fall frost usually arrives about November 15, which leaves 199 frost-free days. An early freeze before October 18 happens one year in ten.

Safe after (10% risk)
May 27
Average first frost
Nov 15
Frost-free season
199 days
Hard freeze (28°F) ends
Apr 8
Next 6 nights in Monrovia

No frost in the next 6 nights

National Weather Service forecast, updated Oct 22, 12:57 UTC

  1. ThuOct 2253°
  2. FriOct 2355°
  3. SatOct 2457°
  4. SunOct 2559°
  5. MonOct 2659°
  6. TueOct 2760°
JanFebMarAprMayJunJulAugSepOctNovDecLast frost Apr 28First frost Nov 15199 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND199 frost-free days
Frost risk through the year at Mount Wilson Cbs, 6.8 miles from Monrovia.

Planting calendar for Monrovia

Windows count forward or back from the average frost dates above. Click a crop for dates across California.

Start indoorsPlant outSow outdoorsFall plantingAverage last and first frost
Warm-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
TomatoesMay 5–May 19
PumpkinsMay 12–May 26
SunflowersApr 28–May 19
CucumbersMay 12–May 19
CornMay 5–May 19
Sweet potatoesMay 19–Jun 2
WatermelonMay 12–May 26
Green beansMay 5–May 26
ZucchiniMay 5–May 19
OkraMay 19–Jun 2
PeppersMay 12–May 26
BasilMay 5–May 19
Butternut squashMay 5–May 19
CantaloupeMay 12–May 26
EggplantMay 12–May 26
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesMar 31–Apr 14
OnionsMar 17–Apr 7
CarrotsApr 7–May 12
LettuceApr 14–May 5
BroccoliMar 31–Apr 14
BeetsMar 31–May 12
PeasMar 17–Mar 31
CabbageMar 31–Apr 14
RadishesMar 24–May 5
Brussels sproutsApr 14–Apr 28
SpinachMar 17–Apr 7
CilantroApr 14–May 5
KaleMar 31–Apr 14
Collard greensMar 31–Apr 14
TurnipsMar 31–Apr 14
DillApr 28–May 12
CeleryMay 5–May 12
CauliflowerApr 14–Apr 28
LeeksApr 14–Apr 28
Swiss chardApr 14–May 12
ParsleyApr 14–May 5
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsNov 1–Dec 6
GarlicOct 25–Nov 29
Daffodil bulbsOct 18–Nov 29
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesMar 31–Apr 14
AsparagusMar 31–Apr 14

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FMar 31Apr 28May 27Oct 18Nov 15Dec 9
Hard freeze, 28°FFeb 28Apr 8May 10Nov 5Dec 4Dec 29

Read the spring 10% column as the date after which only one year in ten still gets frost. That is the safer date for tomatoes, peppers and basil.

Where these numbers come from

NOAA station Mount Wilson Cbs (USC00046006) sits 6.8 miles from the center of Monrovia at 5,710 feet. Its averages cover 1991 to 2020. Low spots, valleys and open fields can keep getting frost a week or two after the station stops; city centers and lakeshores usually get less of it.

Questions

When is the last frost in Monrovia, CA?

The average last frost date in Monrovia is April 28, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 27.

When is the first frost in Monrovia?

The first frost in fall usually comes around November 15. One year in ten it arrives before October 18.

How long is the growing season in Monrovia?

About 199 days between the average last and first frost.

When should I plant tomatoes in Monrovia?

Plant tomato seedlings outside from May 5 to May 19. Start seeds indoors six to eight weeks earlier.

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