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 2026-07-01.

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% 38%	141550
	Night	7% 9% 4 10% 6% 6% 5% 4 6% 8% 36%	139552
Transparency	Day	43% 7% 16% 24% 10% 1	141256
	Night	45% 6% 15% 23% 10% 1	139431
Seeing	Day	13% 9% 28% 30% 16% 4	18112
	Night	12% 7% 30% 35% 13% 2	27457

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% 12% 5% 17% 9% 9% 6% 5% 6% 5% 20%	3985
	11th to 20th	Day	4 7% 3 10% 10% 11% 10% 5% 7% 9% 26%	4119
	21st to end	Day	5% 10% 4 13% 8% 5% 6% 4 6% 9% 29%	5165
February	1st to 10th	Day	7% 12% 5% 14% 8% 7% 8% 6% 8% 7% 19%	1727
	11th to 20th	Day	6% 11% 5% 10% 8% 6% 6% 6% 7% 7% 27%	1845
	21st to end	Day	5% 10% 4 14% 9% 8% 7% 6% 6% 7% 26%	1640
March	1st to 10th	Day	6% 12% 4 14% 8% 7% 7% 4 6% 7% 24%	4600
	11th to 20th	Day	5% 14% 6% 17% 7% 5% 4 3 4 7% 26%	4938
	21st to end	Day	11% 11% 4 9% 6% 5% 5% 5% 5% 7% 33%	5979
April	1st to 10th	Day	7% 10% 4 8% 6% 5% 6% 4 7% 7% 37%	2520
	11th to 20th	Day	12% 12% 5% 9% 6% 4 4 5% 6% 7% 30%	2550
	21st to end	Day	12% 11% 3 8% 5% 4 5% 3 6% 7% 36%	2940
May	1st to 10th	Day	11% 8% 2 6% 4 3 4 3 5% 7% 46%	8224
	11th to 20th	Day	14% 9% 3 8% 6% 5% 6% 5% 7% 8% 30%	8191
	21st to end	Day	10% 7% 2 6% 4 5% 5% 4 5% 7% 45%	9603
June	1st to 10th	Day	14% 7% 2 6% 5% 5% 6% 4 7% 8% 36%	3360
	11th to 20th	Day	21% 7% 3 7% 5% 5% 5% 4 6% 8% 29%	3360
	21st to end	Day	13% 5% 2 6% 6% 5% 5% 5% 7% 9% 38%	3360
July	1st to 10th	Day	6% 4 2 5% 4 4 5% 4 7% 9% 49%	7161
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 5% 7% 9% 44%	6780
	21st to end	Day	6% 4 1 4 3 4 4 4 6% 9% 54%	7012
August	1st to 10th	Day	10% 5% 2 5% 5% 5% 5% 4 6% 7% 46%	4552
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 49%	4483
	21st to end	Day	11% 4 2 5% 3 3 3 3 5% 7% 53%	4477
September	1st to 10th	Day	10% 5% 2 5% 3 4 5% 3 6% 8% 49%	2400
	11th to 20th	Day	14% 6% 2 7% 5% 4 5% 4 5% 7% 41%	2400
	21st to end	Day	10% 6% 1 4 3 3 4 3 5% 7% 52%	2144
October	1st to 10th	Day	8% 8% 2 6% 3 5% 4 4 6% 8% 45%	3270
	11th to 20th	Day	8% 7% 2 5% 4 4 5% 5% 8% 12% 40%	3126
	21st to end	Day	7% 8% 4 9% 5% 6% 5% 5% 6% 7% 37%	3190
November	1st to 10th	Day	17% 14% 4 9% 5% 4 4 4 5% 6% 29%	1653
	11th to 20th	Day	7% 15% 6% 13% 8% 7% 6% 4 5% 5% 25%	1680
	21st to end	Day	8% 13% 6% 10% 8% 8% 7% 5% 4 5% 26%	1471
December	1st to 10th	Day	5% 12% 5% 13% 9% 8% 7% 5% 6% 7% 23%	2268
	11th to 20th	Day	6% 14% 7% 15% 8% 8% 8% 4 6% 7% 18%	2319
	21st to end	Day	4 8% 3 14% 8% 7% 5% 4 5% 9% 34%	3058
January	1st to 10th	Night	5% 11% 5% 16% 9% 7% 6% 4 7% 8% 21%	8904
	11th to 20th	Night	3 7% 4 13% 9% 8% 7% 5% 8% 8% 26%	8779
	21st to end	Night	5% 9% 4 11% 8% 7% 6% 5% 6% 9% 31%	9046
February	1st to 10th	Night	7% 11% 5% 12% 9% 6% 6% 5% 6% 8% 25%	2912
	11th to 20th	Night	4 10% 4 12% 7% 5% 6% 5% 6% 8% 33%	2662
	21st to end	Night	3 8% 4 9% 8% 7% 7% 5% 7% 9% 33%	2165
March	1st to 10th	Night	5% 11% 6% 14% 7% 7% 7% 6% 7% 8% 23%	5494
	11th to 20th	Night	6% 11% 4 12% 7% 6% 5% 4 6% 9% 30%	5272
	21st to end	Night	9% 10% 5% 10% 6% 5% 5% 4 7% 8% 30%	5220
April	1st to 10th	Night	6% 8% 3 7% 5% 4 6% 4 7% 8% 42%	2100
	11th to 20th	Night	11% 12% 4 10% 5% 4 4 4 5% 7% 33%	2018
	21st to end	Night	12% 9% 4 8% 5% 5% 5% 5% 6% 7% 35%	1680
May	1st to 10th	Night	11% 7% 2 6% 4 4 4 3 5% 6% 47%	4724
	11th to 20th	Night	16% 10% 3 9% 5% 5% 5% 4 6% 7% 30%	4702
	21st to end	Night	11% 7% 2 6% 4 4 5% 4 6% 8% 43%	4584
June	1st to 10th	Night	11% 5% 2 7% 4 3 3 4 6% 9% 45%	1260
	11th to 20th	Night	17% 7% 3 6% 4 4 5% 5% 6% 8% 35%	1260
	21st to end	Night	11% 5% 1 5% 5% 4 5% 4 7% 9% 43%	1260
July	1st to 10th	Night	8% 5% 2 5% 3 4 4 4 7% 10% 48%	2783
	11th to 20th	Night	8% 4 1 5% 4 4 5% 4 6% 8% 51%	3180
	21st to end	Night	5% 3 1 4 3 3 4 4 5% 8% 61%	3846
August	1st to 10th	Night	7% 4 1 5% 3 4 5% 4 6% 8% 53%	2608
	11th to 20th	Night	6% 3 1 4 3 5% 5% 5% 7% 10% 50%	2576
	21st to end	Night	8% 4 1 5% 3 4 4 3 6% 8% 53%	3430
September	1st to 10th	Night	10% 4 1 5% 3 4 4 4 5% 9% 51%	2000
	11th to 20th	Night	12% 6% 2 7% 4 4 4 3 5% 7% 45%	2000
	21st to end	Night	9% 5% 2 4 3 3 3 4 6% 7% 54%	2255
October	1st to 10th	Night	10% 7% 2 6% 4 3 4 4 6% 7% 49%	3920
	11th to 20th	Night	6% 6% 2 6% 4 4 4 4 6% 9% 50%	3989
	21st to end	Night	8% 8% 3 7% 4 5% 5% 3 6% 8% 43%	4610
November	1st to 10th	Night	16% 13% 5% 9% 5% 5% 4 4 5% 6% 28%	2860
	11th to 20th	Night	7% 13% 7% 12% 9% 6% 5% 5% 5% 6% 27%	2940
	21st to end	Night	7% 13% 5% 11% 8% 5% 5% 5% 6% 8% 27%	3146
December	1st to 10th	Night	7% 14% 6% 15% 9% 8% 6% 4 6% 6% 19%	5134
	11th to 20th	Night	6% 14% 6% 12% 8% 8% 7% 6% 7% 7% 20%	6093
	21st to end	Night	3 8% 4 11% 9% 7% 5% 4 5% 5% 40%	8140

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	65% 6% 8% 10% 11%	3985
	11th to 20th	Day	52% 7% 15% 18% 7% 1	4140
	21st to end	Day	52% 6% 18% 16% 8%	5165
February	1st to 10th	Day	59% 8% 13% 13% 7%	1727
	11th to 20th	Day	53% 7% 11% 19% 9% 1	1854
	21st to end	Day	55% 7% 12% 18% 8%	1640
March	1st to 10th	Day	58% 8% 16% 11% 7%	4600
	11th to 20th	Day	57% 8% 14% 15% 6%	4939
	21st to end	Day	48% 6% 14% 20% 12%	5979
April	1st to 10th	Day	43% 7% 17% 22% 10% 1	2520
	11th to 20th	Day	51% 8% 14% 18% 8% 2	2550
	21st to end	Day	47% 6% 15% 23% 8% 1	2940
May	1st to 10th	Day	37% 5% 10% 31% 16% 1	8224
	11th to 20th	Day	47% 9% 12% 22% 10% 1	8195
	21st to end	Day	34% 8% 11% 26% 18% 2	9603
June	1st to 10th	Day	43% 8% 14% 23% 11% 1	3360
	11th to 20th	Day	51% 9% 12% 21% 7%	3360
	21st to end	Day	40% 10% 18% 25% 7%	3360
July	1st to 10th	Day	28% 9% 26% 28% 9%	7083
	11th to 20th	Day	34% 7% 17% 34% 6%	6699
	21st to end	Day	25% 8% 20% 34% 12%	6816
August	1st to 10th	Day	35% 8% 21% 27% 9%	4536
	11th to 20th	Day	32% 7% 19% 35% 7%	4525
	21st to end	Day	30% 6% 20% 35% 9%	4476
September	1st to 10th	Day	32% 7% 18% 30% 12% 2	2400
	11th to 20th	Day	42% 7% 16% 26% 9% 1	2400
	21st to end	Day	30% 6% 16% 32% 14% 2	2144
October	1st to 10th	Day	35% 5% 21% 29% 8% 1	3270
	11th to 20th	Day	34% 5% 19% 31% 9% 1	3126
	21st to end	Day	44% 6% 18% 25% 6%	3190
November	1st to 10th	Day	58% 5% 15% 16% 6%	1653
	11th to 20th	Day	61% 7% 14% 13% 5%	1680
	21st to end	Day	59% 7% 14% 16% 4	1471
December	1st to 10th	Day	59% 8% 15% 12% 5%	2268
	11th to 20th	Day	65% 6% 16% 9% 4	2320
	21st to end	Day	48% 5% 11% 19% 13% 4	3058
January	1st to 10th	Night	58% 6% 12% 17% 7%	8905
	11th to 20th	Night	53% 6% 15% 18% 9%	8820
	21st to end	Night	49% 8% 18% 17% 8%	9046
February	1st to 10th	Night	57% 6% 12% 18% 8%	2912
	11th to 20th	Night	48% 5% 13% 23% 11%	2663
	21st to end	Night	45% 7% 15% 24% 9%	2165
March	1st to 10th	Night	54% 9% 18% 13% 5%	5494
	11th to 20th	Night	48% 8% 18% 18% 8%	5272
	21st to end	Night	48% 7% 12% 20% 13%	5220
April	1st to 10th	Night	37% 7% 16% 25% 14% 1	2100
	11th to 20th	Night	49% 6% 12% 19% 11% 3	2018
	21st to end	Night	46% 6% 12% 22% 13% 1	1680
May	1st to 10th	Night	37% 5% 10% 30% 16% 2	4724
	11th to 20th	Night	51% 7% 11% 20% 11% 1	4702
	21st to end	Night	34% 8% 11% 26% 19% 1	4588
June	1st to 10th	Night	34% 7% 15% 28% 13% 2	1260
	11th to 20th	Night	44% 7% 16% 21% 10% 1	1260
	21st to end	Night	36% 7% 20% 27% 9% 1	1260
July	1st to 10th	Night	27% 9% 26% 32% 5%	2752
	11th to 20th	Night	29% 6% 16% 42% 6%	3138
	21st to end	Night	21% 6% 22% 37% 12% 2	3737
August	1st to 10th	Night	28% 7% 22% 32% 11% 1	2600
	11th to 20th	Night	27% 9% 20% 34% 11%	2600
	21st to end	Night	28% 6% 19% 33% 14%	3430
September	1st to 10th	Night	30% 6% 15% 30% 16% 3	2000
	11th to 20th	Night	37% 7% 15% 28% 11% 1	2000
	21st to end	Night	30% 5% 14% 32% 18% 2	2255
October	1st to 10th	Night	34% 6% 18% 33% 9% 1	3920
	11th to 20th	Night	32% 5% 16% 33% 13% 1	3989
	21st to end	Night	39% 6% 18% 30% 7% 1	4610
November	1st to 10th	Night	55% 5% 15% 17% 6% 1	2860
	11th to 20th	Night	58% 6% 16% 14% 5%	2940
	21st to end	Night	54% 7% 16% 18% 4	3146
December	1st to 10th	Night	65% 6% 12% 12% 4	5134
	11th to 20th	Night	60% 6% 17% 12% 4	6091
	21st to end	Night	46% 5% 9% 24% 13% 3	8140

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	12% 8% 31% 28% 16% 5%	220
	11th to 20th	Day	13% 10% 34% 28% 14% 1	220
	21st to end	Day	11% 11% 34% 29% 14% 1	358
February	1st to 10th	Day	12% 12% 36% 27% 12% 2	330
	11th to 20th	Day	11% 6% 28% 34% 16% 5%	330
	21st to end	Day	6% 7% 33% 38% 13% 3	273
March	1st to 10th	Day	13% 9% 35% 28% 13% 3	330
	11th to 20th	Day	10% 13% 35% 27% 13% 2	460
	21st to end	Day	16% 10% 33% 27% 13% 2	594
April	1st to 10th	Day	11% 12% 34% 28% 10% 5%	540
	11th to 20th	Day	16% 14% 31% 27% 10% 3	555
	21st to end	Day	14% 9% 28% 31% 15% 2	750
May	1st to 10th	Day	13% 8% 26% 33% 16% 4	753
	11th to 20th	Day	13% 9% 26% 30% 16% 5%	775
	21st to end	Day	13% 11% 22% 30% 18% 6%	844
June	1st to 10th	Day	13% 15% 28% 25% 14% 5%	780
	11th to 20th	Day	20% 11% 26% 27% 13% 3	780
	21st to end	Day	14% 8% 22% 29% 20% 7%	780
July	1st to 10th	Day	9% 6% 22% 32% 24% 7%	722
	11th to 20th	Day	9% 7% 26% 29% 21% 8%	718
	21st to end	Day	7% 6% 23% 32% 22% 10%	794
August	1st to 10th	Day	10% 6% 22% 32% 22% 8%	726
	11th to 20th	Day	10% 6% 20% 36% 22% 6%	715
	21st to end	Day	12% 8% 23% 31% 20% 6%	583
September	1st to 10th	Day	12% 10% 30% 29% 16% 4	530
	11th to 20th	Day	17% 9% 27% 31% 15% 2	530
	21st to end	Day	15% 8% 31% 31% 13% 1	345
October	1st to 10th	Day	17% 7% 31% 23% 18% 4	330
	11th to 20th	Day	14% 11% 34% 25% 14% 2	330
	21st to end	Day	13% 11% 37% 24% 13% 2	363
November	1st to 10th	Day	22% 9% 32% 25% 10% 3	330
	11th to 20th	Day	14% 13% 38% 26% 7% 1	330
	21st to end	Day	11% 8% 36% 33% 9% 2	330
December	1st to 10th	Day	7% 9% 36% 34% 11% 3	302
	11th to 20th	Day	10% 13% 44% 27% 7%	220
	21st to end	Day	9% 4 37% 30% 17% 3	242
January	1st to 10th	Night	10% 8% 35% 34% 11% 1	1050
	11th to 20th	Night	11% 11% 36% 32% 9% 1	1050
	21st to end	Night	11% 10% 39% 29% 10% 1	1155
February	1st to 10th	Night	11% 9% 33% 32% 14% 1	1022
	11th to 20th	Night	9% 7% 29% 39% 13% 2	824
	21st to end	Night	6% 5% 27% 39% 19% 4	692
March	1st to 10th	Night	12% 7% 31% 37% 13% 1	840
	11th to 20th	Night	9% 7% 34% 35% 13% 1	840
	21st to end	Night	15% 6% 28% 36% 13% 2	754
April	1st to 10th	Night	10% 7% 31% 38% 14% 1	630
	11th to 20th	Night	15% 9% 31% 36% 8% 1	623
	21st to end	Night	17% 9% 29% 36% 10%	630
May	1st to 10th	Night	14% 7% 27% 37% 14% 1	630
	11th to 20th	Night	14% 8% 30% 31% 16% 1	621
	21st to end	Night	16% 8% 23% 34% 16% 3	604
June	1st to 10th	Night	11% 8% 28% 35% 15% 2	420
	11th to 20th	Night	18% 6% 27% 33% 15% 1	420
	21st to end	Night	14% 5% 21% 41% 18% 1	420
July	1st to 10th	Night	6% 5% 19% 44% 24% 1	390
	11th to 20th	Night	11% 4 25% 38% 22% 1	388
	21st to end	Night	5% 4 23% 42% 23% 3	600
August	1st to 10th	Night	8% 4 19% 42% 24% 3	597
	11th to 20th	Night	8% 4 19% 41% 27% 2	594
	21st to end	Night	12% 4 24% 40% 19%	660
September	1st to 10th	Night	11% 4 26% 38% 20% 2	600
	11th to 20th	Night	14% 5% 25% 40% 16% 1	600
	21st to end	Night	11% 8% 30% 37% 12% 1	670
October	1st to 10th	Night	19% 5% 26% 35% 15% 2	800
	11th to 20th	Night	12% 8% 31% 37% 11% 2	853
	21st to end	Night	15% 10% 31% 35% 9% 1	1100
November	1st to 10th	Night	23% 8% 31% 32% 7% 1	1025
	11th to 20th	Night	13% 10% 36% 31% 9% 2	1050
	21st to end	Night	12% 9% 38% 31% 8% 1	1050
December	1st to 10th	Night	10% 6% 35% 33% 12% 3	1050
	11th to 20th	Night	12% 12% 32% 34% 9% 1	1050
	21st to end	Night	10% 6% 32% 36% 14% 3	1155

Page generated at 2026-06-28 00:10:50. Version ac07

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