Weather statistics, phenology and records
Monthly averages, climate normals, phenology, growing degree days and weather records for Hayward - USA.
Highest temperature
90.9 F
11 Jun
Lowest temperature
35.8 F
20 Feb
Total precipitation
1.9 in
38 Rain days
Strongest wind gust
36.0 mph
18 Feb
Monthly averages
| Month | Avg temp | Max temp | Min temp | Precipitation | Rain days |
|---|---|---|---|---|---|
| Jan | -- | -- | -- | -- | -- |
| Feb | 54.9 F | 78.1 F | 35.8 F | 0.4 in | 11 |
| Mar | 62.1 F | 85.3 F | 44.2 F | 0.1 in | 4 |
| Apr | 57.9 F | 77.4 F | 45.5 F | 0.7 in | 17 |
| May | 59.0 F | 81.7 F | 50.0 F | 0.5 in | 4 |
| Jun | 61.9 F | 90.9 F | 52.3 F | 0.1 in | 2 |
| Jul | 63.1 F | 89.1 F | 54.7 F | 0.0 in | 0 |
| Aug | 61.3 F | 79.7 F | 58.3 F | 0.0 in | 0 |
| Sep | 60.6 F | 60.6 F | 60.6 F | 0.0 in | 0 |
| Oct | -- | -- | -- | -- | -- |
| Nov | -- | -- | -- | -- | -- |
| Dec | -- | -- | -- | -- | -- |
Season Tracker 2026
🌸 Spring days
216
Days with T_max ≥ 15°C
☀️ Summer days
25
Days with T_max ≥ 25°C
🔥 Tropical days
4
Days with T_max ≥ 30°C
❄️ Frost days
0
Days with T_min < 0°C
🧊 Ice days
0
Days with T_max < 0°C
🌧️ Precipitation days
38
Days with rain ≥ 0.1 mm
Seasonal milestones
| Milestone | 2026 | Difference |
|---|---|---|
| 🌸 First spring day | 12 Feb | — |
| ☀️ First summer day | 28 Feb | — |
| 🌡️ First tropical day | 11 Jun | — |
| ❄️ Last spring frost | — | — |
| 🍂 First autumn frost | — | — |
| 🧊 First ice day | — | — |
Growing Degree Days (base 10 °C) — Total GDD: 1431
Peak GDD period
Shows daily GDD bars and a 14-day rolling total so warm stretches stand out.
Best 14-day period
12 Jul
– 25 Jul
138.9 GDD
Average per day: 9.9 GDD
What are Growing Degree Days?
Growing Degree Days (GDD) measure accumulated heat above a base temperature — not calendar days.
GDD = max(0, (Tmax + Tmin) / 2 − 10)
Each day contributes a value equal to how many degrees the average temperature exceeds 10 °C. A day with a high of 26 °C and a low of 12 °C contributes (26 + 12) / 2 − 10 = 9 GDD.
The total GDD for a year is the sum of all daily values. A warm summer can easily produce 1 000 – 1 500 GDD, which is why the total is much larger than 365.
Base temperature: 10 °C (growing threshold for most plants in temperate climates).
All-time records
Highest temperature
90.9 F
11 Jun 2026
#2
89.1 F
22 Jul 2026
#3
88.3 F
21 Jul 2026
#4
86.9 F
12 Jun 2026
#5
85.3 F
21 Mar 2026
Lowest temperature
35.8 F
20 Feb 2026
#2
38.8 F
21 Feb 2026
#3
41.2 F
18 Feb 2026
#4
43.7 F
19 Feb 2026
#5
44.2 F
05 Mar 2026
Warmest day (avg)
72.9 F
22 Jul 2026
#2
72.8 F
17 Mar 2026
#3
72.5 F
11 Jun 2026
#4
71.6 F
20 Mar 2026
#5
71.3 F
18 May 2026
Coldest day (avg)
45.4 F
20 Feb 2026
#2
45.5 F
18 Feb 2026
#3
47.6 F
19 Feb 2026
#4
47.7 F
21 Feb 2026
#5
49.3 F
17 Feb 2026
Largest daily range
62.1 F
03 Apr 2026
#2
61.5 F
11 Jun 2026
#3
61.0 F
12 Jun 2026
#4
59.5 F
19 May 2026
#5
58.8 F
21 Mar 2026
Most precipitation (day)
0.3 in
29 May 2026
#2
0.2 in
28 May 2026
#3
0.2 in
10 Apr 2026
#4
0.2 in
16 Feb 2026
#5
0.2 in
21 Apr 2026
Highest rain rate
0.0 in
16 Feb 2026
#2
0.0 in
10 Apr 2026
#3
0.0 in
28 May 2026
#4
0.0 in
11 Feb 2026
#5
0.0 in
12 Feb 2026
Strongest wind gust
36.0 mph
18 Feb 2026
#2
34.0 mph
19 Feb 2026
#3
34.0 mph
20 Feb 2026
#4
30.0 mph
17 Feb 2026
#5
29.0 mph
04 Mar 2026
Highest average wind
10.1 mph
26 May 2026
#2
9.8 mph
06 Jun 2026
#3
9.2 mph
19 Feb 2026
#4
9.2 mph
08 Jul 2026
#5
9.1 mph
11 Feb 2026
Highest pressure
30 inHg
30 May 2026
#2
30 inHg
08 Jul 2026
#3
30 inHg
31 May 2026
#4
30 inHg
03 Jun 2026
#5
30 inHg
07 Jul 2026
Lowest pressure
30 inHg
04 Aug 2026
#2
30 inHg
03 Aug 2026
#3
30 inHg
12 Jun 2026
#4
30 inHg
11 Jun 2026
#5
30 inHg
02 Aug 2026
Highest humidity
88%
09 Jun 2026
#2
87%
27 Jun 2026
#3
86%
04 Jun 2026
#4
86%
13 Jun 2026
#5
86%
24 Jun 2026
Lowest humidity
20%
11 Jun 2026
#2
27%
22 Jul 2026
#3
28%
21 Jul 2026
#4
32%
12 Jun 2026
#5
38%
14 Jul 2026
Highest UV index
7.4
21 Jul 2026
#2
7.3
20 Jul 2026
#3
7.2
19 Jul 2026
#4
6.9
11 Jul 2026
#5
6.8
12 Jul 2026
Highest solar radiation
1318 W/m²
12 May 2026
#2
1248 W/m²
20 Apr 2026
#3
1236 W/m²
19 Jul 2026
#4
1202 W/m²
04 May 2026
#5
1192 W/m²
22 Apr 2026
Most sunshine hours
24 h
16 Aug 2026
#2
24 h
05 Aug 2026
#3
24 h
06 Aug 2026
#4
24 h
07 Aug 2026
#5
24 h
08 Aug 2026
Climate normals vs 2026
Departure from normal
| Month | Normal avg | Actual avg | Departure |
|---|---|---|---|
| Jan | -- | -- | -- |
| Feb | 54.9 F | 54.9 F | 0.0 F |
| Mar | 62.1 F | 62.1 F | 0.0 F |
| Apr | 57.9 F | 57.9 F | 0.0 F |
| May | 59.0 F | 59.0 F | 0.0 F |
| Jun | 61.9 F | 61.9 F | 0.0 F |
| Jul | 63.1 F | 63.1 F | 0.0 F |
| Aug | 61.3 F | 61.3 F | 0.0 F |
| Sep | 60.6 F | 60.6 F | 0.0 F |
| Oct | -- | -- | -- |
| Nov | -- | -- | -- |
| Dec | -- | -- | -- |
Compare periods
vs
vs
Highest temp
Lowest temp
Precipitation
Max wind
No data
Highest temp
Lowest temp
Precipitation
Max wind
No data