Photo: FASTILY · CC BY-SA 4.0Blackhawk reaches 100° on about 11 days a year, more than 91% of U.S. towns
A typical July afternoon reaches 86°, a January night drops to 41°, and snow is almost unheard of.
A year in Blackhawk at a glance
Each month’s typical high and low, and what it brings.
What stands out about Blackhawk’s climate
Compared with towns across the U.S., with Blackhawk’s place in California beside it.
What a year in Blackhawk feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 292 frost-free days a year
In half of years the last 32° night comes by February 15 and the first by December 2. Frost and day counts come from NOAA’s station at Livermore, CA, 10 miles from the town’s center, 490 ft lower.
The 2023 USDA map puts Blackhawk’s center in zone 9b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 27°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 21 inches of rain a year
January is the wettest month and July the driest. Rain falls on about 68 days a year. Snow is rare: about 0.7" in a normal year at Mt Diablo Junction, CA, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Blackhawk
74% of the work is heating. Months averaging under 55° run from November through March.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Livermore, CA.
Living with Blackhawk’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
292 frost-free days in zone 9b. The last frost comes by Feb 15 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Dec 2.
Months with highs of 62–84° and lows of 40° or more: March, April, May, June, September, October and November. 2.4 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Blackhawk from natural hazards, earthquakes are the largest share (55%); heat waves, cold waves, winter storms and ice storms together are 3%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Blackhawk and its neighbors
Danville has the coldest January nights next door (40°, 1° colder). Differences under a degree are within what the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Blackhawk’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Blackhawk, CA | 41° | 86° | 21" | 0.7" |
| Green, OR | 37° | 86° | 32" | 0.0" |
| Sierra Vista Southeast, AZ | 32° | 91° | 15" | 0.7" |
| Alpine, TX | 30° | 90° | 15" | 2.2" |
| College Place, WA | 30° | 91° | 15" | 7.2" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Blackhawk averaged 1.6° warmer than the 1900s. The biggest change is in January (+2.1°).
A bigger shift than in 64% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Blackhawk compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Blackhawk’s place among California’s.
Blackhawk weather by month
Highs, lows and precipitation from NOAA’s grid at Blackhawk’s center; snow, wet days and snow on the ground from Mt Diablo Junction, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 55° | 41° | 4.3" | 0.1" | 12 | 0 | 45° – 55° |
| February | 58° | 43° | 3.9" | 0.5" | 11 | 0 | 45° – 56° |
| March | 63° | 45° | 3.3" | 0.1" | 10 | 0 | 47° – 60° |
| April | 67° | 46° | 1.5" | 0.0" | 7 | 0 | 51° – 61° |
| May | 73° | 51° | 0.7" | 0.0" | 4 | 0 | 55° – 70° |
| June | 81° | 56° | 0.1" | 0.0" | 1 | 0 | 63° – 72° |
| July | 86° | 60° | 0.0" | 0.0" | 0 | 0 | 69° – 78° |
| August | 86° | 61° | 0.0" | 0.0" | 0 | 0 | 70° – 78° |
| September | 83° | 59° | 0.1" | 0.0" | 1 | 0 | 67° – 75° |
| October | 75° | 53° | 1.0" | 0.0" | 3 | 0 | 60° – 72° |
| November | 63° | 46° | 2.1" | 0.0" | 7 | 0 | 48° – 59° |
| December | 55° | 41° | 4.3" | 0.0" | 11 | 0 | 44° – 52° |
| Year | 70° | 50° | 21.4" | 0.7" | 68 | 0 |
How much a month can swing
A normal is an average. May swings the most: from 1991 to 2020 its average ranged from 55° to 70°. December is the most reliable, staying within 8°.
Where Blackhawk’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Blackhawk’s center.
- Snow: Mt Diablo Junction, CA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Livermore, CA, 10 miles from the town’s center, 490 ft lower; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Blackhawk’s climate
What is the weather like in Blackhawk?
A typical July afternoon reaches 86°, a January night drops to 41°, and snow is almost unheard of. Milder January nights than 90% of U.S. towns; hotter July afternoons than 55% of U.S. towns.
How cold does it get in Blackhawk in winter?
December nights average 41°. About 13 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 44°.
How much snow does Blackhawk get?
About 0.7 inches in a normal winter at Mt Diablo Junction, CA, so most winters see none.
How hot does it get in Blackhawk?
July, with a typical high of 86° and a low of 60°. About 57 days a year reach 90° and 11 reach 100° (Livermore, CA).
When is the first and last frost in Blackhawk?
In half of years the last spring frost (32°) comes by February 15 and the first fall frost by December 2, about 292 frost-free days, at Livermore, CA.
What growing zone is Blackhawk in?
Zone 9b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 27°.
What is the best time of year to visit Blackhawk?
By one simple rule (highs of 62–84° and lows of 40° or more), March, April, May, June, September, October and November. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Blackhawk getting warmer?
Yes: 1991–2020 averaged 1.6° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 64% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Blackhawk.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.