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Will it freeze in Diamond Bar in the next 7 nights?
No overnight lows at or below 32°F are forecast in Diamond Bar during the next 7 nights in the available NWS frost forecast.
Tonight: forecast low 56°F. Above 36°F.
NWS forecast period: Thu, Nov 5, 6:00 PM PST to Fri, Nov 6, 6:00 AM PST.
No nights at or below 36°F in the National Weather Service forecast for the next 7 nights.
- Tonight 56°F Above 36°F · Mostly Clear
- Fri, Nov 6 57°F Above 36°F · Clear
- Sat, Nov 7 59°F Above 36°F · Clear
- Sun, Nov 8 61°F Above 36°F · Mostly Clear
- Mon, Nov 9 60°F Above 36°F · Mostly Clear
- Tue, Nov 10 58°F Above 36°F · Mostly Clear
- Wed, Nov 11 57°F Above 36°F · Slight Chance Light Rain
Overnight lows from the National Weather Service forecast for this location. This covers the available forecast window, not the first freeze of the whole season. Frost can form above 32°F on clear, calm nights.
Frost and freeze probabilities
Freeze dates shift from year to year. Spring percentages describe the chance of a freeze after the stated date; fall percentages describe the chance of a freeze by that date. The 10% spring date is the cautious one: a later freeze happens about 1 year in 10.
These dates describe historical probabilities, not this year’s forecast or the earliest and latest possible freezes. Different weather stations or probability thresholds can produce different published dates for the same city.
Average first hard freeze in Diamond Bar
Most years have no 28°F hard freeze at Pomona/fairplex, according to NOAA’s 1991–2020 Climate Normals. Check the short-term forecast above during cold snaps.
| Temperature | Last spring date 90% · 50% · 10% chance of a later freeze | First fall date 10% · 50% · 90% chance of an earlier freeze | Season |
|---|---|---|---|
| 36°F frost possible | Dec 29 · Feb 8 · Mar 9 | Nov 21 · Dec 10 · Dec 26 | 303 days |
| 32°F freeze | Dec 14 · Jan 8 · Feb 18 | Dec 5 · Dec 28 · Feb 2 | 354 days |
| 28°F hard freeze | rare in most years | rare in most years | 365 days |
Average high temperature by month
1991–2020 normals at Pomona/fairplex
Average low temperature by month
Months with lows near or below freezing carry frost risk
Where these frost dates come from
The frost dates for Diamond Bar, CA come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Pomona/fairplex (station USC00047050, elevation 999 ft), 6.3 mi from Diamond Bar. Local conditions (valleys, hilltops, distance to water, city heat) can shift frost dates by days or weeks. The hardiness zone is from the 2023 USDA Plant Hardiness Zone Map (USDA ARS and Oregon State University PRISM). See our methodology.
Frost dates near Diamond Bar
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Walnut, CA | 3.1 mi | Jan 8 | Dec 28 |
| Pomona, CA | 5.0 mi | Jan 8 | Dec 28 |
| Brea, CA | 6.2 mi | Jan 8 | Dec 28 |
| West Covina, CA | 6.2 mi | Jan 8 | Dec 28 |
| Chino Hills, CA | 6.8 mi | Jan 17 | Dec 19 |
| Covina, CA | 7.5 mi | Jan 8 | Dec 28 |
| San Dimas, CA | 7.5 mi | Jan 8 | Dec 28 |
| La Puente, CA | 8.1 mi | rare | rare |
| La Habra Heights, CA | 8.1 mi | rare | rare |
| Yorba Linda, CA | 8.1 mi | Jan 17 | Dec 19 |
Frequently asked questions
When is the last frost in Diamond Bar?
On average, the last spring frost (32°F) in Diamond Bar is around January 8. In about 1 year in 10 it comes after February 18, and in 9 years in 10 it comes after December 14.
When is the first frost in Diamond Bar?
The first fall frost (32°F) usually arrives around December 28. There’s a 10% chance of a freeze by December 5 and a 90% chance by February 2.
Can it frost in Diamond Bar after the last frost date?
Yes. Frost can form on clear, calm nights even when the air stays above 32°F. Temperatures of 36°F or lower, cold enough for frost on exposed plants, have a 50% chance of occurring after February 8.
What growing zone is Diamond Bar?
Diamond Bar is in USDA Plant Hardiness Zone 10a (average annual extreme minimum temperature 30 to 35°F), based on the 2023 USDA map for ZIP code 91765. See growing zones in California.
More: all California frost dates · California growing zones · UV index today in Diamond Bar · frost vs. freeze