About 0.5°F per decade, measured from San Bruno's official daily weather records, 1971–2025. Individual years still bounce around — some recent ones came in cool — but the long-term line has clearly risen.
Is that a lot? San Bruno's warming is broadly in line with other cities in United States — neither unusually fast nor unusually slow.
What has actually changed
Each card compares the 1970s (the first ten years of the
record) with recent years (the last ten) — the same span
the headline and the chart use.
Freezing nights
1 fewer night
1970s
1 / yr
→
Recent
0 / yr
Milder winters — fewer frosts
Average temperature
+1.9°F
1970s
57.2°F
→
Recent
59.1°F
A steady upward drift
Hot days above 90°F
about the same
1970s
5 / yr
→
Recent
5 / yr
About the same number of heat days
Rainy days
4 fewer days
1970s
62 / yr
→
Recent
58 / yr
Drier on average
San Bruno's temperature, year by year
Average temperature for each year from 1971 to 2025.
a warmer-than-average year a cooler-than-average year
Each bar is one year. Most recent years sit above the older ones.
Some recent years still came in cool — warming is a slope,
not a straight climb.
When in the year the change shows up
How much warmer each month is now than in the 1970s.
Useful if you garden or care about a particular season —
otherwise the headline above already has the answer.
January has warmed the most — about 1.8°F. The warming runs across the whole year, not just one season.
Methodology & sources
Temperature — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at San Francisco Intl AP (NOAA GHCN station USW00023234), about 4 km from the city centre.