USDA Hardiness Zone 13a
Frost Dates for 00920 — San Juan, Puerto Rico
NOAA 1991–2020 normals from Rio Piedras Exp Stn, PR (92 ft), 3 miles southeast.
Updated
No night at or below 32°F was recorded at Rio Piedras Exp Stn, PR in 1991–2020, not even 36°F, so San Juan has no frost dates to plan around; the coolest month, February, averages a low of 65°F.
- Winters with a freeze
- 0%
- Winters with 36°F
- 0%
- Coldest month low
- 65°F
- Hardiness zone
- 13a
32°F or below, 1991–2020
frost possible on leaves
average, February
60 to 65°F (15.6 to 18.3°C) coldest night
Frost risk by date in San Juan
Rio Piedras Exp Stn, PR, 3 miles southeast of San Juan, did not record a night at or below 32°F in 1991–2020. All 25 other Puerto Rico stations behind this site's ZIP pages recorded no 32°F night either.
Freeze probabilities 1991–2020 at Rio Piedras Exp Stn, PR, 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 00920 →Compare San Juan with another place →
Weather by month in San Juan
August is the warmest month at Rio Piedras Exp Stn, PR, averaging 90°F by day and 73°F at night; February is the coldest at 86°F and 65°F. Not one month recorded a 32°F night; the lowest monthly average low is 65°F.
Warmth for growing adds up to 10,490 growing degree days a year (base 50°F), more than at 68% of the 25 Puerto Rico stations. 47% of them (4,980) have built up by the end of June, and August adds the most, 987.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 85 | 66 | 0% | 0 | 787 |
| Feb | 86 | 65 | 0% | 0 | 708 |
| Mar | 86 | 66 | 0% | 0 | 804 |
| Apr | 87 | 68 | 0% | 0 | 831 |
| May | 89 | 71 | 0% | 0 | 919 |
| Jun | 90 | 72 | 0% | 0 | 930 |
| Jul | 90 | 72 | 0% | 0 | 964 |
| Aug | 90 | 73 | 0% | 0 | 987 |
| Sep | 90 | 73 | 0% | 0 | 942 |
| Oct | 90 | 72 | 0% | 0 | 952 |
| Nov | 87 | 69 | 0% | 0 | 840 |
| Dec | 86 | 68 | 0% | 0 | 825 |
Monthly normals 1991–2020 at Rio Piedras Exp Stn, PR (92 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, Toa Baja Levittown, PR, 5 miles west of San Juan, has no 32°F night on record either, and a coolest-month low 4°F warmer (69°F).
Where these figures come from
ZIP 00920 is 3 miles from Rio Piedras Exp Stn, PR, which stands at 92 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 13 other ZIP codes share the station; its figures are presented in full for 00926 (San Juan). The 2023 USDA Plant Hardiness Zone Map lists ZIP 00920 in zone 13a, the band where the coldest night of the year averaged 60 to 65°F (15.6 to 18.3°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across Puerto Rico →
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.