Seasonal Water Needs

Want to do your part to save water? Grass needs much less water in April, May and September. Adjust your lawn watering based on Spokane and Kootenai counties seasonal watering needs. A calendar of watering needs was calculated using daily data from local Agrimet Stations for the years 2015, 2016, 2018, 2019, 2020, and 2021. A three-day running average was calculated to estimate how much water you would need to apply to your lawn if you water every three days. Notice how much less water is needed in spring and fall.

Date (April-May)3 Day Average Lawn Watering Needs (inches)
3-Apr0.20
6-Apr0.18
9-Apr0.23
12-Apr0.27
15-Apr0.27
18-Apr0.39
21-Apr0.40
24-Apr0.38
27-Apr0.41
30-Apr0.44
3-May0.49
6-May0.52
9-May0.52
12-May0.55
15-May0.47
18-May0.43
21-May0.48
24-May0.42
27-May0.45
30-May0.57
Date
(June-July)		3 Day Average Lawn Watering Needs (inches)
2-Jun0.50
5-Jun0.59
8-Jun0.49
11-Jun0.46
14-Jun0.54
17-Jun0.51
20-Jun0.55
23-Jun0.54
26-Jun0.60
29-Jun0.63
2-Jul0.60
5-Jul0.65
8-Jul0.63
11-Jul0.55
14-Jul0.59
17-Jul0.60
20-Jul0.59
23-Jul0.63
26-Jul0.61
29-Jul0.62
Date
(Aug-Sep)		3 Day Average Lawn Watering Needs (inches)
1-Aug0.65
4-Aug0.57
7-Aug0.56
10-Aug0.49
13-Aug0.50
16-Aug0.57
19-Aug0.51
22-Aug0.53
25-Aug0.46
28-Aug0.42
31-Aug0.45
3-Sep0.41
6-Sep0.39
9-Sep0.36
12-Sep0.37
15-Sep0.34
18-Sep0.26
21-Sep0.28
24-Sep0.28
27-Sep0.28
30-Sep0.23
Dates
(April-June)		Weekly Average Lawn Need (inches)
4/1 – 4/70.46
4/8-4/140.59
4/15-4/210.89
4/22-4/280.98
4/29-5/51.11
5/6-5/121.25
5/13-5/191.07
5/20-5/261.02
5/27-6/21.24
6/3-6/91.21
6/10-6/161.19
6/17-6/231.28
6/24-6/301.44
Dates
(July-Sep)		Weekly Average Lawn Need (inches)
7/1-7/71.23
7/8-7/141.23
7/15-7/211.23
7/22-7/281.23
7/29-8/41.23
8/5-8/111.23
8/12-8/181.23
8/19-8/251.16
8/26-9/11.01
9/2-9/80.89
9/9-9/150.83
9/16-9/220.64
9/23-9/300.70
MonthsAverage Daily Lawn Need (Inches)
April.11
May.16
June.18
July.21
August.17
September.11

Scheduling in a Box

The red line shows how much extra water you will use if you turn your sprinklers on in March and turn them off in October without adjusting for how much water your lawn needs. To have a healthy lawn and save water, adjust your sprinklers with the changing seasons.

Water schedule in a box

Adjust your sprinkler run time from April-September to give your lawn only what it needs.

Evapotranspiration and Lawn Demand Chart

Figure 1 shows the variability in evapotranspiration (ET) and Lawn ET values. Generally, lawn demand is about 70% of the reference ET. (Data is shown in inches).

Water Demand 3 Day schedule

Figure 2 shows the 3-day watering needs of lawn crop. In only a few cases should a lawn crop demand an amount in excess of 0.6 inches in one watering event.