Watrous
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Watrous clear sky chart from 2005-11-06 to 2025-02-25.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	9% 8% 3 8% 6% 5% 5% 4 6% 8% 37%	111667
	Night	7% 9% 3 9% 6% 6% 5% 4 6% 8% 36%	115665
Transparency	Day	43% 7% 17% 24% 8% 1	111415
	Night	45% 7% 16% 23% 9% 1	115563
Seeing	Day	12% 9% 28% 30% 16% 5%	16188
	Night	12% 7% 30% 36% 14% 2	25758

By Month

Percentage Cloud Cover NW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	6% 14% 5% 16% 9% 8% 7% 5% 6% 6% 18%	3065
	11th to 20th	Day	4 7% 4 10% 10% 11% 8% 5% 7% 8% 26%	3159
	21st to end	Day	6% 11% 5% 14% 7% 5% 6% 4 6% 8% 29%	3981
February	1st to 10th	Day	7% 12% 5% 14% 8% 7% 8% 6% 8% 7% 19%	1645
	11th to 20th	Day	6% 11% 5% 10% 9% 6% 6% 6% 7% 7% 27%	1755
	21st to end	Day	5% 10% 5% 14% 9% 7% 6% 6% 6% 7% 26%	1524
March	1st to 10th	Day	7% 14% 4 12% 8% 8% 8% 4 5% 6% 23%	3130
	11th to 20th	Day	5% 11% 5% 15% 6% 4 4 4 5% 9% 32%	3378
	21st to end	Day	8% 8% 4 8% 7% 6% 6% 5% 6% 8% 36%	4085
April	1st to 10th	Day	7% 10% 4 8% 6% 6% 6% 4 7% 7% 36%	2280
	11th to 20th	Day	13% 12% 5% 9% 6% 4 4 5% 6% 7% 30%	2304
	21st to end	Day	12% 11% 3 8% 5% 4 5% 4 6% 7% 35%	2660
May	1st to 10th	Day	19% 11% 3 6% 4 3 4 3 5% 7% 35%	4430
	11th to 20th	Day	9% 7% 3 8% 6% 5% 6% 5% 7% 9% 36%	4388
	21st to end	Day	13% 8% 3 8% 5% 5% 6% 4 6% 8% 33%	5129
June	1st to 10th	Day	14% 7% 2 6% 5% 5% 5% 4 7% 8% 36%	3040
	11th to 20th	Day	22% 7% 3 7% 5% 5% 5% 4 6% 8% 29%	3040
	21st to end	Day	11% 5% 2 6% 6% 5% 6% 4 7% 9% 39%	3040
July	1st to 10th	Day	6% 4 2 5% 4 5% 5% 5% 8% 10% 47%	5008
	11th to 20th	Day	8% 4 1 4 4 4 5% 5% 7% 9% 49%	4740
	21st to end	Day	4 4 1 4 4 4 4 4 6% 10% 56%	4877
August	1st to 10th	Day	9% 4 2 5% 5% 5% 5% 4 6% 7% 47%	4412
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 49%	4343
	21st to end	Day	12% 5% 2 5% 3 3 3 3 5% 7% 53%	4340
September	1st to 10th	Day	11% 5% 2 5% 3 3 4 3 6% 8% 48%	2280
	11th to 20th	Day	14% 6% 2 7% 5% 4 5% 4 5% 7% 42%	2280
	21st to end	Day	10% 6% 1 4 3 4 4 3 5% 7% 51%	2037
October	1st to 10th	Day	8% 8% 2 6% 4 5% 4 4 6% 8% 45%	3170
	11th to 20th	Day	8% 6% 2 5% 3 4 5% 5% 8% 13% 41%	3030
	21st to end	Day	7% 8% 4 9% 5% 6% 5% 5% 6% 7% 37%	3091
November	1st to 10th	Day	17% 15% 4 9% 5% 5% 3 4 4 6% 28%	1573
	11th to 20th	Day	7% 15% 6% 13% 8% 7% 5% 4 5% 5% 24%	1600
	21st to end	Day	8% 14% 6% 10% 8% 7% 6% 5% 4 5% 26%	1401
December	1st to 10th	Day	5% 12% 5% 12% 9% 8% 7% 5% 6% 7% 24%	2201
	11th to 20th	Day	6% 14% 7% 15% 8% 8% 7% 4 5% 7% 18%	2259
	21st to end	Day	3 7% 3 14% 8% 7% 5% 4 5% 9% 35%	2992
January	1st to 10th	Night	4 11% 5% 16% 10% 8% 6% 4 8% 9% 20%	6876
	11th to 20th	Night	4 8% 4 14% 10% 9% 7% 5% 7% 7% 23%	6739
	21st to end	Night	5% 9% 4 11% 8% 7% 6% 4 6% 9% 30%	6994
February	1st to 10th	Night	8% 11% 4 11% 9% 7% 6% 5% 6% 8% 25%	2774
	11th to 20th	Night	4 10% 4 12% 7% 6% 6% 5% 6% 8% 33%	2532
	21st to end	Night	4 7% 4 10% 8% 7% 7% 4 7% 9% 33%	2023
March	1st to 10th	Night	7% 12% 5% 12% 7% 7% 6% 5% 7% 8% 25%	3734
	11th to 20th	Night	5% 10% 3 9% 6% 5% 5% 5% 7% 10% 35%	3596
	21st to end	Night	6% 8% 3 8% 6% 5% 6% 4 7% 9% 37%	3558
April	1st to 10th	Night	6% 8% 3 7% 5% 3 6% 4 6% 8% 43%	1900
	11th to 20th	Night	11% 13% 4 10% 5% 4 5% 4 5% 7% 33%	1824
	21st to end	Night	13% 9% 4 8% 5% 5% 5% 5% 6% 7% 35%	1520
May	1st to 10th	Night	19% 11% 3 7% 4 4 5% 3 5% 5% 33%	2540
	11th to 20th	Night	11% 7% 3 7% 5% 5% 5% 5% 7% 7% 38%	2518
	21st to end	Night	13% 8% 3 8% 6% 5% 5% 5% 6% 8% 34%	2448
June	1st to 10th	Night	11% 5% 3 7% 4 3 4 4 6% 9% 44%	1140
	11th to 20th	Night	18% 7% 3 6% 4 4 5% 5% 5% 7% 36%	1140
	21st to end	Night	9% 5% 1 5% 5% 4 5% 3 7% 10% 45%	1140
July	1st to 10th	Night	7% 4 1 4 4 4 5% 5% 8% 11% 47%	1949
	11th to 20th	Night	5% 3 1 5% 4 4 4 4 5% 8% 58%	2220
	21st to end	Night	3 2 1 4 3 3 4 4 5% 8% 63%	2682
August	1st to 10th	Night	7% 4 1 5% 3 4 5% 4 5% 8% 54%	2528
	11th to 20th	Night	6% 3 1 4 3 5% 5% 5% 8% 10% 50%	2496
	21st to end	Night	8% 4 1 5% 3 4 4 3 6% 8% 53%	3325
September	1st to 10th	Night	10% 4 1 5% 4 4 5% 4 5% 9% 50%	1900
	11th to 20th	Night	12% 6% 2 7% 4 4 4 3 5% 7% 46%	1900
	21st to end	Night	10% 6% 2 4 3 3 3 4 6% 7% 52%	2142
October	1st to 10th	Night	11% 7% 2 5% 4 3 4 4 6% 7% 48%	3800
	11th to 20th	Night	6% 5% 2 6% 4 4 4 4 6% 9% 50%	3866
	21st to end	Night	8% 8% 3 7% 5% 5% 5% 4 6% 8% 42%	4467
November	1st to 10th	Night	16% 13% 5% 9% 5% 5% 4 4 5% 6% 28%	2720
	11th to 20th	Night	7% 13% 7% 12% 9% 6% 5% 5% 5% 5% 26%	2800
	21st to end	Night	8% 13% 5% 11% 7% 5% 4 5% 6% 8% 28%	2996
December	1st to 10th	Night	7% 14% 6% 15% 9% 8% 6% 4 6% 6% 20%	4981
	11th to 20th	Night	6% 14% 6% 12% 8% 8% 7% 5% 6% 7% 20%	5933
	21st to end	Night	3 7% 3 12% 9% 7% 5% 3 5% 5% 40%	7964

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	64% 6% 10% 12% 7%	3065
	11th to 20th	Day	53% 6% 16% 18% 8%	3180
	21st to end	Day	53% 7% 20% 15% 4	3981
February	1st to 10th	Day	58% 8% 13% 13% 8%	1645
	11th to 20th	Day	54% 7% 11% 19% 9% 1	1764
	21st to end	Day	55% 7% 12% 18% 8%	1524
March	1st to 10th	Day	60% 7% 15% 12% 7%	3130
	11th to 20th	Day	49% 10% 18% 17% 6%	3379
	21st to end	Day	43% 6% 16% 21% 13%	4085
April	1st to 10th	Day	44% 8% 16% 22% 10%	2280
	11th to 20th	Day	52% 8% 13% 18% 8% 2	2304
	21st to end	Day	47% 6% 15% 22% 8% 1	2660
May	1st to 10th	Day	48% 6% 13% 23% 9% 1	4430
	11th to 20th	Day	39% 10% 14% 23% 12% 1	4392
	21st to end	Day	42% 11% 16% 22% 8% 1	5129
June	1st to 10th	Day	43% 8% 14% 23% 11% 1	3040
	11th to 20th	Day	52% 9% 12% 20% 7%	3040
	21st to end	Day	39% 9% 18% 25% 8%	3040
July	1st to 10th	Day	28% 10% 27% 28% 6%	4930
	11th to 20th	Day	29% 7% 18% 37% 9%	4659
	21st to end	Day	22% 8% 20% 38% 12% 1	4723
August	1st to 10th	Day	34% 8% 20% 28% 10%	4396
	11th to 20th	Day	31% 7% 19% 35% 7%	4385
	21st to end	Day	30% 6% 20% 34% 9%	4339
September	1st to 10th	Day	32% 7% 18% 29% 12% 2	2280
	11th to 20th	Day	41% 6% 16% 26% 9% 1	2280
	21st to end	Day	31% 6% 16% 32% 13% 2	2037
October	1st to 10th	Day	36% 5% 21% 29% 8% 1	3170
	11th to 20th	Day	34% 5% 19% 32% 9% 1	3030
	21st to end	Day	44% 6% 19% 25% 6%	3091
November	1st to 10th	Day	59% 5% 15% 15% 6%	1573
	11th to 20th	Day	62% 7% 14% 13% 5%	1600
	21st to end	Day	60% 6% 14% 16% 4	1401
December	1st to 10th	Day	59% 8% 16% 11% 6%	2201
	11th to 20th	Day	65% 6% 16% 9% 3	2260
	21st to end	Day	47% 5% 11% 20% 13% 4	2992
January	1st to 10th	Night	57% 6% 13% 19% 4	6876
	11th to 20th	Night	57% 5% 15% 15% 8%	6780
	21st to end	Night	49% 8% 22% 17% 4	6994
February	1st to 10th	Night	56% 6% 11% 18% 8%	2774
	11th to 20th	Night	48% 6% 13% 22% 11%	2533
	21st to end	Night	44% 7% 15% 24% 9%	2023
March	1st to 10th	Night	52% 9% 17% 17% 4	3734
	11th to 20th	Night	41% 9% 23% 19% 8%	3596
	21st to end	Night	40% 7% 14% 22% 16%	3558
April	1st to 10th	Night	36% 7% 16% 25% 14% 1	1900
	11th to 20th	Night	49% 6% 12% 18% 12% 3	1824
	21st to end	Night	47% 6% 12% 21% 12% 1	1520
May	1st to 10th	Night	51% 6% 10% 22% 10% 1	2540
	11th to 20th	Night	39% 9% 13% 20% 17% 1	2518
	21st to end	Night	40% 11% 15% 25% 8%	2448
June	1st to 10th	Night	34% 7% 15% 28% 13% 2	1140
	11th to 20th	Night	45% 7% 15% 20% 11% 1	1140
	21st to end	Night	34% 7% 20% 28% 10% 1	1140
July	1st to 10th	Night	25% 10% 29% 29% 6%	1918
	11th to 20th	Night	24% 6% 15% 47% 8%	2178
	21st to end	Night	18% 6% 18% 44% 12% 2	2597
August	1st to 10th	Night	28% 7% 22% 32% 11% 1	2520
	11th to 20th	Night	26% 8% 20% 34% 11%	2520
	21st to end	Night	28% 6% 19% 33% 14%	3325
September	1st to 10th	Night	31% 6% 15% 28% 17% 3	1900
	11th to 20th	Night	37% 6% 15% 29% 12% 1	1900
	21st to end	Night	31% 5% 14% 31% 17% 2	2142
October	1st to 10th	Night	35% 6% 18% 33% 8% 1	3800
	11th to 20th	Night	31% 5% 16% 34% 13% 1	3866
	21st to end	Night	39% 6% 18% 29% 7%	4467
November	1st to 10th	Night	56% 5% 15% 17% 6% 1	2720
	11th to 20th	Night	59% 6% 16% 14% 4	2800
	21st to end	Night	54% 7% 16% 18% 4	2996
December	1st to 10th	Night	65% 7% 12% 12% 4	4981
	11th to 20th	Night	61% 6% 17% 12% 4	5931
	21st to end	Night	46% 5% 9% 24% 13% 3	7964

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	13% 8% 32% 27% 17% 5%	200
	11th to 20th	Day	12% 10% 32% 31% 16% 2	200
	21st to end	Day	11% 10% 35% 29% 14% 1	325
February	1st to 10th	Day	12% 11% 35% 28% 12% 2	300
	11th to 20th	Day	11% 5% 29% 34% 15% 6%	300
	21st to end	Day	7% 6% 28% 42% 14% 3	237
March	1st to 10th	Day	14% 9% 33% 28% 13% 3	270
	11th to 20th	Day	10% 12% 35% 28% 13% 2	388
	21st to end	Day	15% 9% 33% 27% 14% 3	506
April	1st to 10th	Day	11% 12% 36% 26% 10% 5%	460
	11th to 20th	Day	18% 13% 29% 26% 11% 3	473
	21st to end	Day	14% 10% 27% 32% 15% 1	650
May	1st to 10th	Day	14% 8% 24% 32% 17% 4	653
	11th to 20th	Day	11% 8% 26% 32% 17% 6%	675
	21st to end	Day	14% 11% 22% 29% 18% 6%	734
June	1st to 10th	Day	13% 13% 28% 26% 15% 4	680
	11th to 20th	Day	22% 12% 25% 25% 14% 3	680
	21st to end	Day	11% 9% 23% 29% 21% 7%	680
July	1st to 10th	Day	9% 5% 22% 32% 24% 8%	671
	11th to 20th	Day	8% 7% 26% 28% 22% 8%	668
	21st to end	Day	7% 6% 23% 33% 21% 10%	739
August	1st to 10th	Day	8% 5% 22% 33% 22% 9%	676
	11th to 20th	Day	10% 5% 19% 35% 24% 6%	665
	21st to end	Day	12% 8% 23% 31% 19% 6%	539
September	1st to 10th	Day	12% 10% 31% 28% 16% 3	490
	11th to 20th	Day	17% 9% 28% 30% 14% 2	490
	21st to end	Day	16% 9% 31% 30% 12% 2	314
October	1st to 10th	Day	18% 7% 30% 21% 20% 4	300
	11th to 20th	Day	13% 11% 33% 26% 15% 2	300
	21st to end	Day	13% 11% 37% 24% 13% 2	330
November	1st to 10th	Day	23% 8% 32% 24% 10% 3	300
	11th to 20th	Day	14% 12% 38% 27% 8% 1	300
	21st to end	Day	11% 8% 36% 33% 8% 3	300
December	1st to 10th	Day	7% 8% 36% 34% 12% 3	275
	11th to 20th	Day	9% 12% 45% 27% 8%	200
	21st to end	Day	8% 4 36% 30% 18% 4	220
January	1st to 10th	Night	10% 8% 35% 34% 11% 1	1000
	11th to 20th	Night	11% 10% 36% 33% 9% 1	1000
	21st to end	Night	11% 10% 39% 30% 9%	1100
February	1st to 10th	Night	12% 8% 33% 33% 14% 1	974
	11th to 20th	Night	9% 6% 30% 40% 13% 3	784
	21st to end	Night	5% 5% 26% 40% 20% 4	646
March	1st to 10th	Night	11% 7% 30% 37% 13% 1	760
	11th to 20th	Night	9% 8% 33% 36% 12% 1	760
	21st to end	Night	14% 7% 27% 37% 14% 2	682
April	1st to 10th	Night	9% 7% 32% 37% 14% 1	570
	11th to 20th	Night	16% 7% 31% 36% 9% 1	563
	21st to end	Night	17% 9% 28% 36% 9%	570
May	1st to 10th	Night	15% 7% 27% 36% 15% 1	570
	11th to 20th	Night	13% 7% 29% 32% 17% 1	561
	21st to end	Night	16% 8% 22% 34% 17% 3	546
June	1st to 10th	Night	11% 7% 28% 37% 16% 2	380
	11th to 20th	Night	19% 6% 27% 31% 16% 1	380
	21st to end	Night	13% 4 20% 43% 19% 1	380
July	1st to 10th	Night	6% 4 19% 44% 25% 1	370
	11th to 20th	Night	10% 4 25% 38% 22% 1	368
	21st to end	Night	5% 4 23% 42% 22% 4	570
August	1st to 10th	Night	8% 4 20% 42% 24% 3	567
	11th to 20th	Night	8% 3 18% 40% 28% 2	564
	21st to end	Night	13% 4 25% 39% 19%	627
September	1st to 10th	Night	11% 4 27% 38% 19% 1	570
	11th to 20th	Night	14% 5% 25% 39% 16% 1	570
	21st to end	Night	12% 8% 30% 37% 12% 1	636
October	1st to 10th	Night	19% 5% 25% 34% 15% 2	760
	11th to 20th	Night	12% 7% 31% 38% 11% 2	810
	21st to end	Night	15% 9% 31% 36% 9% 1	1045
November	1st to 10th	Night	23% 7% 30% 32% 7% 1	975
	11th to 20th	Night	13% 10% 36% 31% 9% 2	1000
	21st to end	Night	12% 9% 38% 31% 8% 1	1000
December	1st to 10th	Night	10% 6% 35% 33% 13% 3	1000
	11th to 20th	Night	12% 11% 31% 35% 10% 1	1000
	21st to end	Night	10% 5% 31% 36% 14% 3	1100

Page generated at 2025-02-22 05:51:35. Version ac07

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