Penticton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Penticton clear sky chart from 2005-11-06 to 2024-11-04.

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	7% 9% 3 8% 5% 5% 5% 4 6% 7% 40%	105835
	Night	7% 11% 4 8% 5% 5% 5% 4 6% 7% 36%	101762
Transparency	Day	43% 9% 13% 20% 12% 3	105598
	Night	46% 8% 13% 20% 10% 2	101645
Seeing	Day	13% 18% 30% 25% 12% 3	15222
	Night	12% 11% 27% 31% 17% 2	23667

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	9% 18% 7% 15% 8% 6% 6% 5% 6% 7% 12%	2539
	11th to 20th	Day	11% 14% 3 9% 8% 5% 5% 4 10% 11% 19%	2516
	21st to end	Day	13% 24% 7% 11% 6% 5% 6% 4 5% 4 15%	2794
February	1st to 10th	Day	6% 15% 4 13% 7% 7% 7% 4 5% 6% 26%	1570
	11th to 20th	Day	6% 12% 6% 12% 8% 6% 6% 4 7% 7% 27%	1665
	21st to end	Day	5% 14% 4 13% 9% 7% 6% 5% 7% 7% 23%	1555
March	1st to 10th	Day	4 13% 5% 12% 7% 6% 7% 5% 7% 9% 26%	3138
	11th to 20th	Day	3 10% 3 7% 5% 5% 5% 4 6% 8% 46%	3325
	21st to end	Day	8% 16% 5% 11% 7% 6% 6% 5% 6% 7% 25%	4124
April	1st to 10th	Day	9% 12% 4 9% 8% 7% 6% 6% 7% 8% 27%	2280
	11th to 20th	Day	7% 12% 3 7% 6% 7% 6% 5% 7% 8% 32%	2262
	21st to end	Day	8% 11% 4 9% 6% 5% 6% 4 6% 9% 31%	2592
May	1st to 10th	Day	7% 10% 3 8% 5% 4 5% 4 6% 8% 41%	4420
	11th to 20th	Day	7% 8% 3 8% 5% 5% 6% 5% 7% 10% 35%	4377
	21st to end	Day	13% 11% 4 10% 6% 6% 6% 5% 6% 7% 26%	4813
June	1st to 10th	Day	14% 8% 3 8% 7% 5% 6% 4 6% 7% 33%	2817
	11th to 20th	Day	13% 8% 3 8% 6% 5% 6% 5% 6% 8% 31%	3012
	21st to end	Day	8% 5% 2 6% 6% 5% 6% 5% 7% 8% 43%	3033
July	1st to 10th	Day	3 2 1 3 3 3 4 3 5% 6% 67%	4713
	11th to 20th	Day	3 2 1 3 3 3 3 3 3 5% 73%	4420
	21st to end	Day	3 3 1 3 3 3 3 3 5% 7% 65%	4790
August	1st to 10th	Day	2 1 1 3 3 3 5% 5% 6% 8% 63%	4401
	11th to 20th	Day	3 2 1 4 3 4 5% 4 7% 9% 58%	4299
	21st to end	Day	6% 3 1 4 4 5% 5% 4 6% 8% 53%	4216
September	1st to 10th	Day	5% 5% 2 5% 4 3 3 4 5% 6% 58%	2280
	11th to 20th	Day	8% 5% 2 5% 5% 5% 6% 5% 6% 6% 48%	2259
	21st to end	Day	8% 7% 3 7% 3 5% 4 4 6% 7% 46%	2074
October	1st to 10th	Day	6% 5% 2 7% 5% 5% 4 4 6% 7% 49%	3180
	11th to 20th	Day	9% 8% 4 8% 6% 6% 5% 4 5% 6% 38%	3072
	21st to end	Day	8% 10% 3 9% 5% 6% 6% 5% 6% 6% 36%	3101
November	1st to 10th	Day	11% 13% 4 10% 7% 6% 6% 5% 6% 8% 25%	1624
	11th to 20th	Day	8% 13% 4 11% 8% 8% 7% 5% 5% 6% 25%	1520
	21st to end	Day	8% 14% 5% 11% 8% 7% 7% 6% 7% 6% 22%	1440
December	1st to 10th	Day	7% 15% 3 12% 8% 8% 7% 6% 7% 7% 21%	1330
	11th to 20th	Day	8% 18% 6% 15% 6% 6% 6% 5% 7% 9% 14%	1682
	21st to end	Day	10% 16% 6% 14% 7% 7% 7% 5% 6% 7% 15%	2602
January	1st to 10th	Night	10% 21% 10% 15% 8% 6% 6% 4 5% 5% 11%	4406
	11th to 20th	Night	8% 16% 5% 10% 7% 5% 4 6% 8% 14% 15%	4382
	21st to end	Night	14% 25% 6% 13% 6% 6% 5% 4 4 4 13%	4862
February	1st to 10th	Night	8% 15% 5% 13% 8% 7% 5% 4 5% 7% 24%	2608
	11th to 20th	Night	7% 15% 4 10% 7% 5% 6% 4 5% 7% 31%	2402
	21st to end	Night	6% 16% 5% 12% 6% 5% 5% 5% 6% 6% 28%	1898
March	1st to 10th	Night	3 9% 4 11% 7% 8% 7% 5% 8% 8% 29%	3736
	11th to 20th	Night	4 9% 3 7% 5% 4 4 4 6% 8% 48%	3651
	21st to end	Night	7% 13% 4 10% 6% 7% 5% 4 7% 8% 28%	3529
April	1st to 10th	Night	7% 10% 3 7% 5% 6% 5% 5% 6% 9% 35%	1900
	11th to 20th	Night	6% 8% 3 7% 6% 5% 6% 5% 7% 8% 37%	1868
	21st to end	Night	8% 10% 2 8% 6% 6% 5% 5% 6% 8% 37%	1587
May	1st to 10th	Night	8% 8% 2 6% 4 4 5% 4 6% 7% 47%	2540
	11th to 20th	Night	5% 6% 1 6% 3 5% 5% 5% 7% 11% 45%	2516
	21st to end	Night	9% 7% 2 6% 5% 6% 6% 4 7% 9% 38%	2762
June	1st to 10th	Night	10% 9% 2 7% 5% 4 5% 4 6% 9% 38%	1359
	11th to 20th	Night	11% 7% 2 7% 5% 5% 4 5% 7% 8% 41%	1163
	21st to end	Night	6% 4 1 5% 5% 4 4 4 7% 7% 52%	1142
July	1st to 10th	Night	3 2 1 3 2 2 3 3 4 4 73%	2242
	11th to 20th	Night	2 1 1 2 2 3 3 3 4 5% 75%	2540
	21st to end	Night	2 2 1 3 3 3 3 2 4 7% 71%	2762
August	1st to 10th	Night	2 2 1 4 3 4 4 4 5% 6% 65%	2529
	11th to 20th	Night	2 2 1 3 3 4 4 4 7% 11% 59%	2527
	21st to end	Night	6% 4 2 5% 4 4 5% 5% 6% 7% 53%	3461
September	1st to 10th	Night	5% 3 1 4 3 3 4 4 5% 7% 61%	1900
	11th to 20th	Night	6% 5% 2 5% 3 4 3 3 5% 8% 54%	1920
	21st to end	Night	7% 6% 3 7% 4 4 4 4 6% 8% 48%	2104
October	1st to 10th	Night	7% 5% 2 6% 4 5% 5% 4 6% 7% 50%	3800
	11th to 20th	Night	13% 8% 3 7% 4 4 4 4 6% 7% 40%	3862
	21st to end	Night	9% 10% 3 9% 5% 5% 5% 4 5% 6% 39%	4457
November	1st to 10th	Night	12% 15% 4 8% 6% 6% 6% 4 7% 7% 25%	2526
	11th to 20th	Night	8% 14% 5% 11% 7% 6% 6% 5% 6% 7% 26%	2660
	21st to end	Night	8% 16% 5% 11% 8% 7% 8% 5% 6% 7% 20%	2719
December	1st to 10th	Night	7% 16% 6% 13% 7% 6% 6% 4 6% 8% 21%	2850
	11th to 20th	Night	10% 19% 6% 13% 8% 6% 7% 5% 7% 6% 13%	3510
	21st to end	Night	10% 21% 6% 12% 8% 7% 6% 4 7% 6% 14%	5082

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	69% 10% 9% 9% 2	2539
	11th to 20th	Day	54% 9% 15% 14% 3 6%	2540
	21st to end	Day	71% 8% 9% 8% 3	2794
February	1st to 10th	Day	59% 10% 12% 12% 6% 1	1570
	11th to 20th	Day	58% 10% 13% 12% 6% 1	1674
	21st to end	Day	61% 10% 12% 12% 5%	1555
March	1st to 10th	Day	54% 11% 10% 13% 11% 1	3138
	11th to 20th	Day	38% 8% 19% 30% 5%	3325
	21st to end	Day	57% 13% 12% 10% 9%	4124
April	1st to 10th	Day	57% 12% 13% 13% 4 1	2280
	11th to 20th	Day	54% 11% 10% 17% 8% 1	2262
	21st to end	Day	51% 11% 11% 17% 9% 1	2592
May	1st to 10th	Day	39% 12% 10% 25% 13% 1	4420
	11th to 20th	Day	40% 12% 16% 23% 8%	4380
	21st to end	Day	53% 12% 11% 20% 5%	4814
June	1st to 10th	Day	52% 9% 10% 15% 10% 4	2817
	11th to 20th	Day	52% 11% 12% 18% 7%	3012
	21st to end	Day	39% 11% 15% 20% 14% 1	3033
July	1st to 10th	Day	19% 5% 8% 21% 29% 17%	4639
	11th to 20th	Day	17% 3 8% 17% 35% 20%	4345
	21st to end	Day	20% 5% 12% 26% 27% 11%	4639
August	1st to 10th	Day	20% 6% 10% 29% 29% 6%	4384
	11th to 20th	Day	24% 6% 20% 34% 13% 3	4341
	21st to end	Day	31% 6% 18% 28% 16% 1	4215
September	1st to 10th	Day	28% 7% 16% 28% 17% 4	2280
	11th to 20th	Day	36% 9% 11% 24% 17% 3	2259
	21st to end	Day	38% 8% 19% 21% 12% 2	2074
October	1st to 10th	Day	39% 6% 17% 32% 6%	3180
	11th to 20th	Day	49% 6% 11% 27% 7%	3072
	21st to end	Day	50% 7% 16% 20% 6%	3101
November	1st to 10th	Day	59% 11% 12% 13% 6%	1624
	11th to 20th	Day	59% 12% 11% 13% 5% 1	1520
	21st to end	Day	59% 10% 14% 12% 5% 1	1440
December	1st to 10th	Day	55% 10% 15% 16% 4	1330
	11th to 20th	Day	62% 13% 12% 8% 5%	1684
	21st to end	Day	66% 11% 10% 9% 4	2602
January	1st to 10th	Night	74% 7% 9% 8% 2	4406
	11th to 20th	Night	53% 8% 12% 15% 7% 5%	4420
	21st to end	Night	73% 7% 8% 8% 3	4862
February	1st to 10th	Night	59% 8% 13% 12% 6% 1	2608
	11th to 20th	Night	54% 7% 14% 17% 7% 1	2404
	21st to end	Night	57% 9% 14% 13% 7%	1898
March	1st to 10th	Night	49% 11% 12% 16% 12%	3736
	11th to 20th	Night	37% 6% 19% 31% 7%	3652
	21st to end	Night	53% 12% 13% 16% 7%	3529
April	1st to 10th	Night	45% 14% 18% 17% 5%	1900
	11th to 20th	Night	46% 10% 13% 19% 11%	1868
	21st to end	Night	45% 9% 13% 23% 10%	1587
May	1st to 10th	Night	34% 7% 12% 31% 14% 1	2540
	11th to 20th	Night	27% 11% 21% 32% 8% 1	2516
	21st to end	Night	39% 13% 16% 28% 5%	2762
June	1st to 10th	Night	44% 9% 12% 21% 12% 2	1359
	11th to 20th	Night	41% 9% 15% 24% 10% 1	1163
	21st to end	Night	29% 12% 16% 27% 14% 2	1142
July	1st to 10th	Night	15% 5% 7% 26% 31% 16%	2207
	11th to 20th	Night	13% 5% 8% 17% 38% 20%	2492
	21st to end	Night	16% 3 12% 31% 26% 11%	2674
August	1st to 10th	Night	22% 4 8% 28% 33% 4	2521
	11th to 20th	Night	19% 5% 23% 35% 16% 2	2551
	21st to end	Night	30% 6% 18% 30% 15% 2	3461
September	1st to 10th	Night	23% 8% 14% 31% 20% 4	1900
	11th to 20th	Night	28% 9% 12% 27% 20% 4	1920
	21st to end	Night	34% 9% 17% 26% 11% 2	2104
October	1st to 10th	Night	38% 5% 18% 29% 10%	3800
	11th to 20th	Night	46% 5% 11% 26% 11%	3862
	21st to end	Night	48% 6% 15% 25% 7%	4457
November	1st to 10th	Night	58% 9% 13% 13% 6% 1	2526
	11th to 20th	Night	58% 9% 14% 12% 5% 2	2660
	21st to end	Night	61% 10% 12% 11% 5% 1	2719
December	1st to 10th	Night	58% 9% 12% 17% 4	2850
	11th to 20th	Night	68% 10% 11% 7% 3	3507
	21st to end	Night	64% 13% 10% 9% 4	5082

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	16% 22% 29% 20% 11% 3	180
	11th to 20th	Day	15% 17% 30% 23% 12% 3	180
	21st to end	Day	17% 19% 36% 21% 7% 1	198
February	1st to 10th	Day	14% 22% 42% 18% 4	230
	11th to 20th	Day	12% 22% 38% 21% 5% 1	365
	21st to end	Day	13% 20% 38% 19% 9% 1	375
March	1st to 10th	Day	15% 27% 30% 19% 7% 1	460
	11th to 20th	Day	11% 25% 27% 23% 11% 2	460
	21st to end	Day	17% 25% 30% 18% 9% 1	506
April	1st to 10th	Day	24% 23% 28% 16% 7% 2	460
	11th to 20th	Day	16% 27% 27% 17% 9% 3	452
	21st to end	Day	16% 22% 32% 18% 9% 2	460
May	1st to 10th	Day	13% 22% 32% 22% 10% 2	463
	11th to 20th	Day	15% 14% 29% 25% 14% 3	488
	21st to end	Day	15% 16% 27% 24% 15% 3	529
June	1st to 10th	Day	15% 17% 28% 27% 11% 2	647
	11th to 20th	Day	16% 18% 30% 23% 11% 2	842
	21st to end	Day	9% 12% 30% 28% 19% 2	863
July	1st to 10th	Day	6% 12% 32% 33% 15% 2	657
	11th to 20th	Day	6% 14% 28% 32% 16% 4	484
	21st to end	Day	5% 10% 29% 36% 15% 6%	531
August	1st to 10th	Day	5% 8% 26% 35% 19% 6%	487
	11th to 20th	Day	5% 9% 29% 31% 19% 7%	477
	21st to end	Day	8% 17% 27% 28% 14% 6%	539
September	1st to 10th	Day	9% 16% 30% 25% 15% 6%	490
	11th to 20th	Day	11% 15% 28% 25% 16% 4	490
	21st to end	Day	15% 20% 32% 19% 10% 3	490
October	1st to 10th	Day	14% 20% 27% 23% 12% 3	490
	11th to 20th	Day	16% 19% 26% 25% 10% 3	439
	21st to end	Day	16% 18% 33% 24% 7% 1	330
November	1st to 10th	Day	20% 20% 29% 26% 5%	242
	11th to 20th	Day	17% 25% 29% 19% 8% 2	180
	21st to end	Day	15% 21% 28% 21% 13% 3	180
December	1st to 10th	Day	16% 16% 24% 22% 18% 4	180
	11th to 20th	Day	13% 20% 34% 22% 8% 2	180
	21st to end	Day	13% 15% 34% 29% 7% 2	198
January	1st to 10th	Night	17% 16% 33% 24% 9% 1	760
	11th to 20th	Night	14% 12% 33% 29% 10% 2	760
	21st to end	Night	12% 13% 33% 30% 11% 2	836
February	1st to 10th	Night	15% 13% 33% 28% 9% 2	760
	11th to 20th	Night	12% 9% 32% 34% 11% 1	744
	21st to end	Night	11% 14% 28% 29% 17% 1	628
March	1st to 10th	Night	11% 12% 31% 26% 18% 2	760
	11th to 20th	Night	9% 13% 31% 30% 15% 1	760
	21st to end	Night	11% 13% 29% 32% 14% 1	836
April	1st to 10th	Night	11% 13% 25% 34% 15% 3	760
	11th to 20th	Night	10% 11% 32% 28% 17% 1	740
	21st to end	Night	11% 11% 33% 30% 14% 1	447
May	1st to 10th	Night	10% 9% 26% 36% 18% 1	380
	11th to 20th	Night	11% 4 19% 39% 26% 2	374
	21st to end	Night	13% 7% 21% 32% 26% 2	411
June	1st to 10th	Night	13% 8% 26% 39% 14% 1	380
	11th to 20th	Night	13% 8% 26% 35% 18% 1	380
	21st to end	Night	6% 6% 25% 38% 24% 2	380
July	1st to 10th	Night	5% 5% 18% 41% 30% 1	370
	11th to 20th	Night	4 6% 23% 40% 26% 2	368
	21st to end	Night	4 5% 17% 43% 30% 2	416
August	1st to 10th	Night	4 3 14% 37% 38% 3	378
	11th to 20th	Night	5% 1 16% 36% 38% 5%	393
	21st to end	Night	6% 5% 20% 38% 29% 3	812
September	1st to 10th	Night	6% 6% 21% 36% 28% 4	760
	11th to 20th	Night	8% 6% 16% 32% 29% 9%	760
	21st to end	Night	11% 7% 23% 34% 22% 3	760
October	1st to 10th	Night	13% 7% 20% 33% 24% 3	760
	11th to 20th	Night	12% 12% 24% 34% 17% 2	760
	21st to end	Night	17% 11% 29% 29% 12% 3	836
November	1st to 10th	Night	18% 12% 33% 28% 7% 1	754
	11th to 20th	Night	17% 17% 28% 24% 12% 1	760
	21st to end	Night	15% 15% 31% 27% 10% 3	819
December	1st to 10th	Night	13% 14% 29% 31% 11% 2	950
	11th to 20th	Night	16% 14% 34% 27% 8% 1	950
	21st to end	Night	18% 14% 34% 26% 8%	965

Page generated at 2024-11-01 19:47:35. Version ac07

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